Dynamic TDD uplink/downlink configuration using DCI

ABSTRACT

The invention relates to a method for dynamically indicating a TDD reconfiguration to the mobile station by encoding the dynamic TDD re-configuration indication into the DCI or CRC calculated for the DCI. In one embodiment, the TDD configuration indication is implicitly encoded as an RNTI into the CRC, when scrambling the CRC for the DCI with a TDD-RNTI. In another embodiment, the TDD configuration indication is part of the DCI payload, while the CRC for the DCI is scrambled with a cell identifier, identifying the target cell for which the dynamic TDD re-configuration is to be applied. In still another embodiment, the TDD configuration indication is part of the DCI payload, where the DCI payload further includes an invalid parameter indicating to the mobile station that the DCI carries the TDD configuration indication.

BACKGROUND

Technical Field

The invention relates to methods for indicating a Time Division Duplexuplink/downlink configuration for a mobile station. The invention isalso providing the mobile station and the base station for participatingin the methods described herein.

Description of the Related Art

Long Term Evolution (LTE)

Third-generation mobile systems (3G) based on WCDMA radio-accesstechnology are being deployed on a broad scale all around the world. Afirst step in enhancing or evolving this technology entails introducingHigh-Speed Downlink Packet Access (HSDPA) and an enhanced uplink, alsoreferred to as High Speed Uplink Packet Access (HSUPA), giving a radioaccess technology that is highly competitive.

In order to be prepared for further increasing user demands and to becompetitive against new radio access technologies, 3GPP introduced a newmobile communication system which is called Long Term Evolution (LTE).LTE is designed to meet the carrier needs for high speed data and mediatransport as well as high capacity voice support for the next decade.The ability to provide high bit rates is a key measure for LTE.

The work item (WI) specification on Long-Term Evolution (LTE) calledEvolved UMTS Terrestrial Radio Access (UTRA) and UMTS Terrestrial RadioAccess Network (UTRAN) is finalized as Release 8 (LTE Rel. 8). The LTEsystem represents efficient packet-based radio access and radio accessnetworks that provide full IP-based functionalities with low latency andlow cost. In LTE, scalable multiple transmission bandwidths arespecified such as 1.4, 3.0, 5.0, 10.0, 15.0, and 20.0 MHz, in order toachieve flexible system deployment using a given spectrum. In thedownlink, Orthogonal Frequency Division Multiplexing (OFDM) based radioaccess was adopted because of its inherent immunity to multipathinterference (MPI) due to a low symbol rate, the use of a cyclic prefix(CP) and its affinity to different transmission bandwidth arrangements.Single-carrier frequency division multiple access (SC-FDMA) based radioaccess was adopted in the uplink, since provisioning of wide areacoverage was prioritized over improvement in the peak data rateconsidering the restricted transmit power of the user equipment (UE).Many key packet radio access techniques are employed includingmultiple-input multiple-output (MIMO) channel transmission techniquesand a highly efficient control signaling structure is achieved in LTERel. 8/9.

LTE Architecture

The overall architecture is shown in FIG. 1 and a more detailedrepresentation of the E-UTRAN architecture is given in FIG. 2. TheE-UTRAN consists of an eNodeB, providing the E-UTRA user plane(PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towardsthe user equipment (UE). The eNodeB (eNB) hosts the Physical (PHY),Medium Access Control (MAC), Radio Link Control (RLC) and Packet DataControl Protocol (PDCP) layers that include the functionality ofuser-plane header-compression and encryption. It also offers RadioResource Control (RRC) functionality corresponding to the control plane.It performs many functions including radio resource management,admission control, scheduling, enforcement of negotiated uplink Qualityof Service (QoS), cell information broadcast, ciphering/deciphering ofuser and control plane data, and compression/decompression ofdownlink/uplink user plane packet headers. The eNodeBs areinterconnected with each other by means of the X2 interface.

The eNodeBs are also connected by means of the S1 interface to the EPC(Evolved Packet Core), more specifically to the MME (Mobility ManagementEntity) by means of the S1-MME and to the Serving Gateway (SGW) by meansof the S1-U. The S1 interface supports a many-to-many relation betweenMMEs/Serving Gateways and eNodeBs. The SGW routes and forwards user datapackets, while also acting as the mobility anchor for the user planeduring inter-eNodeB handovers and as the anchor for mobility between LTEand other 3GPP technologies (terminating S4 interface and relaying thetraffic between 2G/3G systems and PDN GW). For idle state userequipments, the SGW terminates the downlink data path and triggerspaging when downlink data arrives for the user equipment. It manages andstores user equipment contexts, e.g., parameters of the IP bearerservice, network internal routing information. It also performsreplication of the user traffic in case of lawful interception.

The MME is the key control-node for the LTE access-network. It isresponsible for idle mode user equipment tracking and paging procedureincluding retransmissions. It is involved in the beareractivation/deactivation process and is also responsible for choosing theSGW for a user equipment at the initial attach and at time of intra-LTEhandover involving Core Network (CN) node relocation. It is responsiblefor authenticating the user (by interacting with the HSS). TheNon-Access Stratum (NAS) signaling terminates at the MME and it is alsoresponsible for generation and allocation of temporary identities touser equipments. It checks the authorization of the user equipment tocamp on the service provider's Public Land Mobile Network (PLMN) andenforces user equipment roaming restrictions. The MME is the terminationpoint in the network for ciphering/integrity protection for NASsignaling and handles the security key management. Lawful interceptionof signaling is also supported by the MME. The MME also provides thecontrol plane function for mobility between LTE and 2G/3G accessnetworks with the S3 interface terminating at the MME from the SGSN. TheMME also terminates the S6a interface towards the home HSS for roaminguser equipments.

Component Carrier Structure in LTE (Release 8)

The downlink component carrier of a 3GPP LTE (Release 8 and further) issubdivided in the time-frequency domain in so-called subframes. In 3GPPLTE (Release 8 and further) each subframe is divided into two downlinkslots as shown in FIG. 3, wherein the first downlink slot comprises thecontrol channel region (PDCCH region) within the first OFDM symbols.Each subframe consists of a give number of OFDM symbols in the timedomain (12 or 14 OFDM symbols in 3GPP LTE, Release 8 and further),wherein each OFDM symbol spans over the entire bandwidth of thecomponent carrier. The OFDM symbols thus each consists of a number ofmodulation symbols transmitted on respective N_(RB) ^(DL)×N_(sc) ^(RB)subcarriers as also shown in FIG. 4.

Assuming a multi-carrier communication system, e.g., employing OFDM, asfor example used in 3GPP Long Term Evolution (LTE), the smallest unit ofresources that can be assigned by the scheduler is one “resource block”.A physical resource block (PRB) is defined as N_(symb) ^(DL) consecutiveOFDM symbols in the time domain (e.g., 7 OFDM symbols) and N_(sc) ^(RB)consecutive subcarriers in the frequency domain as exemplified in FIG. 4(e.g., 12 subcarriers for a component carrier). In 3GPP LTE (Release 8),a physical resource block thus consists of N_(symb) ^(DL)×N_(sc) ^(RB)resource elements, corresponding to one slot in the time domain and 180kHz in the frequency domain (for further details on the downlinkresource grid, see for example 3GPP TS 36.211, “Evolved UniversalTerrestrial Radio Access (E-UTRA); Physical Channels and Modulation(Release 8)”, section 6.2, available at http://www.3gpp.org andincorporated herein by reference).

One subframe consists of two slots, so that there are 14 OFDM symbols ina subframe when a so-called “normal” CP (cyclic prefix) is used, and 12OFDM symbols in a subframe when a so-called “extended” CP is used. Forsake of terminology, in the following the time-frequency resourcesequivalent to the same N_(sc) ^(RB) consecutive subcarriers spanning afull subframe is called a “resource block pair”, or equivalent “RB pair”or “PRB pair”.

The term “component carrier” refers to a combination of several resourceblocks in the frequency domain. In future releases of LTE, the term“component carrier” is no longer used; instead, the terminology ischanged to “cell”, which refers to a combination of downlink andoptionally uplink resources. The linking between the carrier frequencyof the downlink resources and the carrier frequency of the uplinkresources is indicated in the system information transmitted on thedownlink resources.

Similar assumptions for the component carrier structure apply to laterreleases too.

Logical and Transport Channels

The MAC layer provides a data transfer service for the RLC layer throughlogical channels. Logical channels are either Control Logical Channelswhich carry control data such as RRC signaling, or Traffic LogicalChannels which carry user plane data. Broadcast Control Channel (BCCH),Paging Control channel (PCCH), Common Control Channel (CCCH), MulticastControl Channel (MCCH) and Dedicated Control Channel (DCCH) are ControlLogical Channels. Dedicated Traffic channel (DTCH) and Multicast TrafficChannel (MTCH) are Traffic Logical Channels.

Data from the MAC layer is exchanged with the physical layer throughTransport Channels. Data is multiplexed into transport channelsdepending on how it is transmitted over the air. Transport channels areclassified as downlink or uplink as follows. Broadcast Channel (BCH),Downlink Shared Channel (DL-SCH), Paging Channel (PCH) and MulticastChannel (MCH) are downlink transport channels, whereas the Uplink SharedChannel (UL-SCH) and the Random Access Channel (RACH) are uplinktransport channels.

A multiplexing is then performed between logical channels and transportchannels in the downlink and uplink respectively.

Layer 1/Layer 2 (L1/L2) Control Signaling

In order to inform the scheduled users about their allocation status,transport format and other data-related information (e.g., HARQinformation, transmit power control (TPC) commands), L1/L2 controlsignaling is transmitted on the downlink along with the data. L1/L2control signaling is multiplexed with the downlink data in a subframe,assuming that the user allocation can change from subframe to subframe.It should be noted that user allocation might also be performed on a TTI(Transmission Time Interval) basis, where the TTI length can be amultiple of the subframes. The TTI length may be fixed in a service areafor all users, may be different for different users, or may even bydynamic for each user. Generally, the L1/2 control signaling needs onlybe transmitted once per TTI. Without loss of generality, the followingassumes that a TTI is equivalent to one subframe.

The L1/L2 control signaling is transmitted on the Physical DownlinkControl Channel (PDCCH). A PDCCH carries a message as a Downlink ControlInformation (DCI), which in most cases includes resource assignments andother control information for a mobile terminal or groups of UEs. Ingeneral, several PDCCHs can be transmitted in one subframe.

It should be noted that in 3GPP LTE, assignments for uplink datatransmissions, also referred to as uplink scheduling grants or uplinkresource assignments, are also transmitted on the PDCCH.

Generally, the information sent on the L1/L2 control signaling forassigning uplink or downlink radio resources (particularly LTE(-A)Release 10) can be categorized to the following items:

-   -   User identity, indicating the user that is allocated. This is        typically included in the checksum by masking the CRC with the        user identity;    -   Resource allocation information, indicating the resources        (Resource Blocks, RBs) on which a user is allocated. Note, that        the number of RBs on which a user is allocated can be dynamic;    -   Carrier indicator, which is used if a control channel        transmitted on a first carrier assigns resources that concern a        second carrier, i.e., resources on a second carrier or resources        related to a second carrier;    -   Modulation and coding scheme that determines the employed        modulation scheme and coding rate;    -   HARQ information, such as a new data indicator (NDI) and/or a        redundancy version (RV) that is particularly useful in        retransmissions of data packets or parts thereof;    -   Power control commands to adjust the transmit power of the        assigned uplink data or control information transmission;    -   Reference signal information such as the applied cyclic shift        and/or orthogonal cover code index, which are to be employed for        transmission or reception of reference signals related to the        assignment;    -   Uplink or downlink assignment index that is used to identify an        order of assignments, which is particularly useful in TDD        systems;    -   Hopping information, e.g., an indication whether and how to        apply resource hopping in order to increase the frequency        diversity;    -   CSI request, which is used to trigger the transmission of        channel state information in an assigned resource; and    -   Multi-cluster information, which is a flag used to indicate and        control whether the transmission occurs in a single cluster        (contiguous set of RBs) or in multiple clusters (at least two        non-contiguous sets of contiguous RBs). Multi-cluster allocation        has been introduced by 3GPP LTE-(A) Release 10.

It is to be noted that the above listing is non-exhaustive, and not allmentioned information items need to be present in each PDCCHtransmission depending on the DCI format that is used.

Downlink control information occurs in several formats that differ inoverall size and also in the information contained in its fields. Thedifferent DCI formats that are currently defined for LTE are as followsand described in detail in 3GPP TS 36.212, “Multiplexing and channelcoding”, section 5.3.3.1 (available at http://www.3gpp.org andincorporated herein by reference). For further information regarding theDCI formats and the particular information that is transmitted in theDCI, please refer to the technical standard or to LTE—The UMTS Long TermEvolution—From Theory to Practice, Edited by Stefanie Sesia, IssamToufik, Matthew Baker, Chapter 9.3, incorporated herein by reference.

Format 0: DCI Format 0 is used for the transmission of resource grantsfor the PUSCH, using single-antenna port transmissions in uplinktransmission mode 1 or 2.

Format 1: DCI Format 1 is used for the transmission of resourceassignments for single codeword PDSCH transmissions (downlinktransmission modes 1, 2 and 7).

Format 1A: DCI Format 1A is used for compact signaling of resourceassignments for single codeword PDSCH transmissions, and for allocatinga dedicated preamble signature to a mobile terminal for contention-freerandom access.

Format 1B: DCI Format 1B is used for compact signaling of resourceassignments for PDSCH transmissions using closed loop precoding withrank-1 transmission (downlink transmission mode 6). The informationtransmitted is the same as in Format 1A, but with the addition of anindicator of the precoding vector applied for the PDSCH transmission.

Format 1C: DCI Format 1C is used for very compact transmission of PDSCHassignments. When format 1C is used, the PDSCH transmission isconstrained to using QPSK modulation.

This is used, for example, for signaling paging messages and broadcastsystem information messages.

Format 1D: DCI Format 1D is used for compact signaling of resourceassignments for PDSCH transmission using multi-user MIMO. Theinformation transmitted is the same as in Format 1B, but instead of oneof the bits of the precoding vector indicators, there is a single bit toindicate whether a power offset is applied to the data symbols. Thisfeature is needed to show whether or not the transmission power isshared between two UEs. Future versions of LTE may extend this to thecase of power sharing between larger numbers of UEs.

Format 2: DCI Format 2 is used for the transmission of resourceassignments for PDSCH for closed-loop MIMO operation.

Format 2A: DCI Format 2A is used for the transmission of resourceassignments for PDSCH for open-loop MIMO operation. The informationtransmitted is the same as for Format 2, except that if the eNodeB hastwo transmit antenna ports, there is no precoding information, and forfour antenna ports two bits are used to indicate the transmission rank.

Format 2B: Introduced in Release 9 and is used for the transmission ofresource assignments for PDSCH for dual-layer beamforming.

Format 2C: Introduced in Release 10 and is used for the transmission ofresource assignments for PDSCH for closed-loop single-user or multi-userMIMO operation with up to 8 layers.

Format 2D: introduced in Release 11 and is used for up to 8 layertransmissions; mainly used for COMP (Cooperative Multipoint)

Format 3 and 3A: DCI formats 3 and 3A are used for the transmission ofpower control commands for PUCCh and PUSCH with 2-bit or 1-bit poweradjustments respectively. These DCI formats contain individual powercontrol commands for a group of UEs.

Format 4: DCI format 4 is used for the scheduling of the PUSCH, usingclosed-loop spatial multiplexing transmissions in uplink transmissionmode 2.

The following table gives an overview of some available DCI formats andthe typical number of bits, assuming for illustration purposes a systembandwidth of 50 RBs and four antennas at the eNodeB. The number of bitsindicated in the right column include the bits for the CRC of theparticular DCI.

DCI Number of bits format Purpose including CRC 0 PUSCH grants 43 1PDSCH assignments with a single codeword 47 1A PDSCH assignments using acompact format 43 1B PDSCH assignments for rank-1 transmission 46 1CPDSCH assignments using a very compact 29 format 1D PDSCH assignmentsfor multi-user MIMO 46 2 PDSCH assignments for closed-loop MIMO 62operation 2A PDSCH assignments for open-loop MIMO 58 operation 2B PDSCHassignments for dual-layer 57 beamforming 2C PDSCH assignments forclosed-loop 58 single-user or multiuser MIMO operation 2D PDSCHassignments for closed-loop 61 single-user or multi-user MIMO operation,COMP 3 Transmit Power Control (TPC) commands 43 for multiple users forPUCCH and PUSCH with 2-bit power adjustments 3A Transmit Power Control(TPC) commands 43 for multiple users for PUCCH and PUSCH with 1-bitpower adjustments 4 PUSCH grants 52

FIG. 5 illustrates the processing structure for one DCI, according to3GPP TS 36.212 FIG. 5.3.3.1, as follows:

-   -   Information element multiplexing (refers to the multiplexing of        the particular information elements making up the one DCI)    -   CRC attachment    -   Channel coding    -   Rate matching

In order that the UE can identify whether it has received a PDCCHtransmission correctly, error detection is provided by means of a 16-bitCRC appended to each PDCCH (i.e., DCI). Furthermore, it is necessarythat the UE can identify which PDCCH(s) are intended for it. This couldin theory be achieved by adding an identifier to the PDCCH payload;however, it turns out to be more efficient to scramble the CRC with the“UE identity”, which saves the additional overhead. The CRC may becalculated and scrambled as defined in detail by 3GPP in TS 36.212,Section 5.3.3.2 “CRC attachment”, incorporated hereby by reference. Thesection describes how error detection is provided on DCI transmissionsthrough a Cyclic Redundancy Check (CRC). A brief summary is given below.

The entire payload is used to calculate the CRC parity bits. The paritybits are computed and attached. In the case where UE transmit antennaselection is not configured or applicable, after attachment, the CRCparity bits are scrambled with the corresponding RNTI.

The scrambling may further depend on the UE transmit antenna selection,as apparent from 36.212. In the case where UE transmit antenna selectionis configured and applicable, after attachment, the CRC parity bits arescrambled with an antenna selection mask and the corresponding RNTI. Asin both cases the RNTI is involved in the scrambling operation, forsimplicity and without loss of generality the following description ofthe embodiments simply refers to the CRC being scrambled (anddescrambled, as applicable) with an RNTI, which should therefore beunderstood as notwithstanding, e.g., a further element in the scramblingprocess such as an antenna selection mask.

Correspondingly, the UE descrambles the CRC by applying the “UEidentity” and, if no CRC error is detected, the UE determines that PDCCHcarries its control information intended for itself. The terminology of“masking” and “de-masking” is used as well, for the above-describedprocess of scrambling a CRC with an identity.

The “UE identity” mentioned above with which the CRC of the DCI may bescrambled can also be a SI-RNTI (System Information Radio NetworkTemporary Identifier), which is not a “UE identity” as such, but ratheran identifier associated with the type of information that is indicatedand transmitted, in this case the system information. The SI-RNTI isusually fixed in the specification and thus known a priori to all UEs.

There are various types of RNTIs that are used for different purposes.The following tables taken from 3GPP 36.321 Chapter 7.1 shall give anoverview of the various 16-bits RNTIs and their usages.

Value (hexa-decimal) RNTI 0000 N/A 0001-003C RA-RNTI, C-RNTI,Semi-Persistent Scheduling C- RNTI, Temporary C-RNTI, TPC-PUCCH-RNTI andTPC-PUSCH-RNTI (see note) 003D-FFF3 C-RNTI, Semi-Persistent SchedulingC-RNTI, Temporary C-RNTI, TPC-PUCCH-RNTI and TPC- PUSCH-RNTI FFF4-FFFCReserved for future use FFFD M-RNTI FFFE P-RNTI FFFF SI-RNTI

Transport Usage Channel Logical Channel Paging and System InformationPCH PCCH change notification Broadcast of System Information DL-SCH BCCHMCCH Information change notification N/A N/A Random Access ResponseDL-SCH N/A Contention Resolution (when no valid DL-SCH CCCH C-RNTI isavailable) Msg3 transmission UL-SCH CCCH, DCCH, DTCH Dynamicallyscheduled unicast UL-SCH DCCH, DTCH transmission Dynamically scheduledunicast DL-SCH CCCH, DCCH, transmission DTCH Triggering of PDCCH orderedrandom N/A N/A access Semi-Persistently scheduled unicast DL-SCH, DCCH,DTCH transmission (activation, UL-SCH reactivation and retransmission)Semi-Persistently scheduled unicast N/A N/A transmission (deactivation)Physical layer Uplink power control N/A N/A Physical layer Uplink powercontrol N/A N/APhysical Downlink Control Channel (PDCCH) andPhysical Downlink Shared Channel (PDSCH)

The physical downlink control channel (PDCCH) carries, e.g., schedulinggrants for allocating resources for downlink or uplink datatransmission.

Each PDCCH is transmitted using one or more so called Control ChannelElements (CCEs). Each CCE corresponds to a set of Resource Elements(REs). In 3GPP LTE, at the moment one CCE consists of 9 Resource ElementGroups (REGs), where one REG consists of four consecutive REs(consecutive in the frequency domain) excluding potential REs ofreference signals. The resource elements occupied by reference symbolsare not included within the REGs, which means that the total number ofREGs in a given OFDM symbol depends on whether or not reference signalsare present.

The PDCCH for the user equipments is transmitted on the first N_(symb)^(PDCCH) OFDM symbols (usually either 1, 2 or 3 OFDM symbols asindicated by the PCFICH, in exceptional cases either 2, 3, or 4 OFDMsymbols as indicated by the PCFICH) within a subframe, extending overthe entire system bandwidth; the system bandwidth is typicallyequivalent to the span of a cell or component carrier. The regionoccupied by the first N_(symb) ^(PDCCH) OFDM symbols in the time domainand the N_(RB) ^(DL)×N_(sc) ^(RB) subcarriers in the frequency domain isalso referred to as PDCCH region or control channel region. Theremaining N_(symb) ^(PDSCH)=2·N_(symb) ^(DL)−N_(symb) ^(PDCCH) OFDMsymbols in the time domain on the N_(RB) ^(DL)×N_(sc) ^(RB) subcarriersin the frequency domain is referred to as the PDSCH region or sharedchannel region (see below).

For a downlink grant on the physical downlink shared channel (PDSCH),the PDCCH assigns a PDSCH resource for (user) data within the samesubframe. The PDCCH control channel region within a subframe consists ofa set of CCE where the total number of CCEs in the control region ofsubframe is distributed throughout time and frequency control resource.Multiple CCEs can be combined to effectively reduce the coding rate ofthe control channel. CCEs are combined in a predetermined manner using atree structure to achieve different coding rate.

In 3GPP LTE a PDCCH can aggregate 1, 2, 4 or 8 CCEs. The number of CCEsavailable for control channel assignment is a function of severalfactors, including carrier bandwidth, number of transmit antennas,number of OFDM symbols used for control and the CCE size, etc. MultiplePDCCHs can be transmitted in a subframe.

On a transport channel level, the information transmitted via the PDCCHis also referred to as L1/L2 control signaling. L1/L2 control signalingis transmitted in the downlink for each user equipment (UE). The controlsignaling is commonly multiplexed with the downlink (user) data in asubframe (assuming that the user allocation can change from subframe tosubframe).

Time Division Duplex—TDD

LTE can operate in Frequency-Division-Duplex (FDD) andTime-Division-Duplex (TDD) modes in a harmonized framework, designedalso to support the evolution of TD-SCDMA (Time-Division SynchronousCode Division Multiple Access). TDD separates the uplink and downlinktransmissions in the time domain, while the frequency may stay the same.

The term “duplex” refers to bidirectional communication between twodevices, distinct from unidirectional communication. In thebidirectional case, transmissions over the link in each direction maytake place at the same time (“full duplex”) or at mutually exclusivetimes (“half duplex”).

For TDD in the unpaired radio spectrum, the basic structure of RBs andREs is depicted in FIG. 4, but only a subset of the subframes of a radioframe are available for downlink transmissions; the remaining subframesare used for uplink transmissions, or for special subframes whichcontain a guard period to allow for switching between the downlink anduplink transmission. The guard period allows the uplink transmissiontiming to be advanced. This TDD structure is known as “Frame StructureType 2” in 3GPP LTE Release 8 and later, of which seven differentconfigurations are defined, which allow a variety of downlink-uplinkratios and switching periodicities. FIG. 6 illustrates the Table withthe 7 different TDD uplink downlink configurations, indexed from 0-6. Ascan be seen therefrom, the seven available TDD uplink-downlinkconfigurations can provide between 40% and 90% of downlink subframes(when counting a special subframe as a downlink subframe, since part ofsuch a subframe is available for downlink transmission).

FIG. 7 shows the frame structure type 2, particularly for a 5 msswitch-point periodicity, i.e., for TDD configurations 0, 1, 2 and 6.

FIG. 7 illustrates a radio frame, being 10 ms in length, and thecorresponding two half-frames of 5 ms each. The radio frame consists of10 subframes with 1 ms, where each of the subframes is assigned the typeof uplink, downlink or special, as defined by the table of FIG. 6, where“D” means Downlink, “U” means Uplink and “S” means Special.

As can be appreciated from FIG. 6, subframe #1 is always a Specialsubframe, and subframe #6 is a Special subframe for TDD configurations0, 1, 2 and 6; for TDD configurations 3, 4 and 5, subframe #6 isdestined for downlink. Special subframes include three fields: DwPTS(Downlink Pilot Time Slot), the GP (Guard Period) and of UpPTS (UplinkPilot Time Slot). The following Table shows information on the specialsubframe and in particular lists the lengths of DwPTS (Downlink PilotTime Slot), the GP (Guard Period) and of UpPTS (Uplink Pilot Time Slot)as a multiple of the sample time T_(s)=(1/30720) ms as defined for 3GPPLTE Release 11.

Normal cyclic prefix in downlink Extended cyclic prefix in downlinkUpPTS UpPTS Special Normal Extended Normal Extended subframe cyclicprefix cyclic prefix cyclic prefix cyclic prefix configuration DwPTS inuplink in uplink DwPTS in uplink in uplink 0  6592 · T_(s) 2192 · T_(s)2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 1 19760 · T_(s)20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 · T_(s) 25600 ·T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 · T_(s) 5  6592 ·T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 · T_(s) 23040 ·T_(s) 7 21952 · T_(s) 12800 · T_(s) 8 24144 · T_(s) — — — 9 13168 ·T_(s) — — —

The TDD configuration applied in the system has an impact on manyoperations performed at the mobile station and base station, such asradio resource management (RRM) measurements, channel state information(CSI) measurements, channel estimations, PDCCH detection and HARQtimings.

In particular, the UE reads the system information to learn about theTDD configuration in its current cell, i.e., which subframe to monitorfor measurement, for CSI measure and report, for time domain filteringto get channel estimation, for PDCCH detection, or for UL/DL ACK/NACKfeedback.

Shortcoming of Current Semi-Static TDD UL/DL Configuration Scheme

Currently, LTE TDD allows for asymmetric UL-DL allocations by providingseven different semi-statically configured uplink-downlinkconfigurations. The current mechanism for adapting UL-DL allocation isbased on the system information acquisition procedure or the systeminformation change procedure, where the TDD UL-DL configuration isindicated by a SIB, particularly the TDD-config parameter in SIB1. (fordetails on the broadcast of system information, 3GPP TS 25.331, “RadioResource Control (RRC)”, version 6.7.0, section 8.1.1, incorporatedherein by reference; available at http://www.3gpp.org).

With the Release 8 system information change procedure, the supportedtime scale for a TDD UL/DL re-configuration is every 640 ms or larger.When re-using the ETWS (Earthquake and Tsunami Warning System), thesupported time scale for TDD UL-DL re-configuration is every 320 ms orlarger depending on the configured default paging cycle.

The semi-static allocation of the TDD UL/DL configuration may or may notmatch the instantaneous traffic situation. However, it would beadvantageous to adapt the TDD UL/DL configuration to the current trafficneeds; for instance, in order to dynamically create more blank uplinksubframes to mitigate interference to the communication, e.g., in uplinkor downlink of a neighboring cell. Correspondingly, it is expected thatRelease 12 will adopt a more dynamic change of the TDD UL/DLconfiguration.

3GPP launched a study item TR 36.828 v11.0.0 to study the time scales ofvarious types of TDD UL/DL re-configurations and their benefits anddisadvantages. In general, the study item concluded that faster TDDUL/DL re-configuration time scales provide larger benefits than slowerTDD UL/DL re-configuration time scales. Further, the amount of requiredspecification changes varies depending on the supported re-configurationtime scales.

The study item however also identified problems for legacy UEs (UEsconformant to only earlier than Release 12 standards that do notimplement the dynamic TDD re-configuration mechanism) stemming fromdifferent TDD configurations for different UEs. In particular, it isassumed that when the base station wants to dynamically reconfigure theTDD configuration for UEs in a cell, the dynamic TDD re-configurationcould only be processed properly by the new UEs; in case the existingSIB-based TDD configuration indication method is not used but a moredynamic indication method, the legacy UEs would not apply the TDDre-configuration. Therefore, the legacy UEs will still assume thepresence of reference signals, e.g., CRS (Common Reference Symbol) indownlink subframes of the radio frame according to the default (i.e.,the SIB-indicated) TDD configuration. In case the dynamic TDDconfiguration has an uplink subframe instead of a downlink subframe, thelegacy UE would thus wrongly assume the CRS to be present, which maylead to wrong measurement and channel estimations.

The study item also considered RRC, MAC and PHY signaling as moredynamic indication methods. TDD UL/DL re-configuration by RRC signalingis in the order of 200 ms and requires a re-configuration message perRRC-connected user, unless a broadcast or a multicast approach isspecified. TDD UL/DL re-configuration by MAC Control Element (CE)signaling in the MAC header is the order of a few tens of ms. Using thePhysical layer design, such as provided by the L1/L2 control signalingof DCI, a time scale of TDD UL/DL adaptation in the order of 10 ms canbe achieved.

In view of the results of the above study item, a TDD UL/DLre-configuration should be performed as fast as possible, thus allowingfor a flexible adaptation of the TDD UL/DL configuration to the trafficsituations.

BRIEF SUMMARY

One object of the invention is to provide an improved Time DivisionDuplex configuration indication, that solves the problems of the priorart as discussed above. A dynamic adaptation of the TDD configuration ofone or more radio frames should be preferably possible.

The object is solved by the subject matter of the independent claims.Advantageous embodiments are subject to the dependent claims.

According to various embodiments of the invention, the Time DivisionDuplex (TDD) configuration to be used for communication between themobile station and the base station is encoded by the base station intoa DCI transmission to the mobile station. In this context, the term DCItransmission is to be understood as the whole transmission, which inthis particular case means the DCI and the corresponding error detectioncode (such as CRC). The invention provides various embodiments on howthis can be achieved.

According to a first aspect of the invention, the TDD configuration isencoded into the error detection code calculated for the DCI; moreparticularly, the specific TDD configuration is implicitly encoded intothe error detection code. For each of the assignable TDD configurationsa different identifier value is defined, and both the mobile stationsand the base stations know the pre-defined identifier values and theassociations with the possible TDD configurations. In more detail, inLTE communication systems the identifier can be a radio networktemporary identifier having a length of 16 bit, which is then scrambledwith the 16-bit error detection code (CRC).

Correspondingly, when the base station wants to dynamically change thedefault TDD configuration to a different target TDD configuration for aparticular cell, it will generate a DCI, will calculate a correspondingerror detection code for the DCI, and then scramble the calculated CRCwith that identifier which is associated with the target TDDconfiguration the mobile station(s) in that cell shall use for the nextradio frame(s).

The DCI itself (i.e., not the CRC) may be either according to a DCIformat already defined in the LTE standards or equivalently having thesame size as an already defined DCI format, such as of Format 1C, or maybe according to a “new” DCI format, which serves the purpose of beingused in connection with the dynamic TDD re-configuration.

In case an already defined LTE DCI is used (such as of format 1C), thenthe base station can set one or more of the parameters in the DCI (incase of Format 1C, the resource block assignment for example) to aninvalid value, such that the mobile station processing the DCI and theinvalid parameter, may easily determine that the received DCI is not a“conventional” DCI Format 1C assigning downlink resources, but rather isused to convey the TDD configuration for dynamic TDD re-configuration.

The first aspect may be further improved in that the above-mentionedinvalid parameter of a defined DCI Format (e.g., DCI format 1C) can beused to encode a further parameter as will be explained. It is assumedthat the invalid parameter can not only take one invalid value butvarious invalid values. In said case, the invalid parameter may be usedto encode the indication that the DCI (with said invalid parameter) iscarrying the dynamic TDD re-configuration, as well as to encode afurther parameter (value).

Specifically, the fact that the parameter is set to any or a group ofthe invalid values allows the mobile station to determine the DCI to bea DCI carrying the TDD configuration indication, and not theconventional DCI. Then, each (or a group) of the invalid values of saidparameter may be then associated with a different value of anotherparticular parameter. For example, the actually-available invalid valuesmay be associated with the different TDD configurations, such that theinvalid parameter, and particularly one of the invalid value of theparameter, also indicates the desired TDD configuration index for thedynamic TDD UL/DL reconfiguration.

Furthermore, a DCI Format already defined by 3GPP can be re-used, namelyby taking the same bit size as the already defined DCI, but defining adifferent content (information elements) within the DCI for particularsituations. For example, the DCI Format 1C of the 3GGP standard TS36.212 can be extended, such that for one set of cases the DCI Format 1Cis used as already defined by 3GPP (for PDSCH assignments), but for theremaining (other) cases the DCI Format 1C is not as intended by 3GPP sofar (as defined at the time of filing the application, respectively),but for the purpose of the dynamic TDD re-configuration according to theinvention.

As the third alternative, a new DCI Format can be defined, possibly witha different length compared to existing DCI formats; the length dependson the further content (parameters) that is to be included in said newDCI format. As will be explained in further detail below, in any case(“defined”, “defined-extended” and “new” DCI) the DCI may include atleast one additional parameter that can be used advantageously togetherwith the dynamic TDD re-configuration.

In accordance with the above, the mobile station receiving the DCI andthe corresponding error detection code will try descrambling andperforming the error detection check on the error detection code usingthe various identifiers pre-defined for the various TDD configurations.When the mobile station successfully performs the error detection checkwith one of the various candidate identifiers, the mobile station willthen determine the specific TDD configuration associated with the oneidentifier for which the error detection check was successful. Themobile station then knows the TDD configuration which is to be appliedfor the next radio frame(s) in its cell.

Furthermore, the mobile station may determine the above-mentionedadditional parameter(s) to gain further advantages; details arepresented in the detailed description chapter.

According to a second aspect of the invention, instead of implicitlyencoding the TDD configuration into the error detection code as in thefirst aspect, the TDD configuration is directly encoded as a parameterin the DCI. Correspondingly, the DCI generated by the base stationcomprises a field (preferably up to 3 bit long) indicating the TDDconfiguration which shall be applied instead of the default TDDconfiguration. The second aspect of the invention further specifies thatthe error detection code, calculated for the DCI and transmittedtogether with the DCI from the base station to the mobile station, isscrambled with a cell identifier, which allows the mobile station toidentify the target cell for which the TDD configuration shall apply.

The mobile station when receiving the DCI and scrambled error detectioncode from the base station, first performs an error detection check onthe error detection code and the DCI, which includes the step ofdescrambling the error detection code. The mobile station performs theerror check until determining the cell identifier actually used for thescrambling process of the error detection code in the base station.

From the determined cell identifier, the mobile station first learnsthat the DCI is a DCI for transporting the TDD configuration (and notany other kind of DCI); secondly, the mobile station learns which targetcell (identified by the cell identifier) the TDD configuration (includedin the DCI) actually is supposed to be applied to. From the DCI payload,the mobile station learns the TDD configuration.

Naturally, the mobile station applies the determined TDD configurationonly in case it is belonging to the determined target cell identified bythe cell identifier used for scrambling the error detection code for theDCI.

The second aspect may be used advantageously for a scenario in whichthere is one macro cell and various small cells; e.g., the macro cell isoperated with frequency division duplex and the small cells with timedivision duplex. The mobile station is located in the macro cell as wellas the small cell. It is assumed that the DCI (and error correctioncode) is transmitted from a base station of the macro cell, but for thepurpose of dynamically changing the TDD configuration of one (or more)of the small cells.

For that purpose the cell identifier used for scrambling the errordetection code for the DCI, may identify only one of the cells, forwhich the new TDD configuration shall apply. Alternatively, varioussmall cells may be grouped together, and associated with a single cell(group) identifier, such that, upon receiving a DCI and error detectioncode scrambled with said single cell (group) identifier, the mobilestations may determine for which cell(s) the new TDD configuration shallapply and for which not.

Although as explained above the use of such a cell identifier forscrambling the error detection code already allows the mobile station toidentify the DCI to be carrying a TDD configuration, the DCI may furthercomprise an invalid parameter to lower the false alarm risk.Specifically, when the base station generates a DCI for dynamicallychanging the TDD configuration of one (or more) cells, a TDDconfiguration parameter is included as well as parameter of the DCI isset to an invalid value. Which particular parameter is to be set to aninvalid value, is less important as long as the mobile station mayidentify said parameter being invalid and thus deriving therefrom thatthe DCI is not a “conventional” DCI, but one carrying a TDDconfiguration. Correspondingly, the mobile station can gather from boththe cell identifier used in connection with the error detection code, aswell as from the invalid parameter of the DCI, that the DCI shallcomprise further an indication as to the new TDD configuration whichshall be applied.

One example for the invalid parameter, is the resource block assignmentparameter of DCI Format 1C, as defined by 3GPP. The resource blockassignment parameter is set to an invalid value of, e.g., all “1”s.

As already explained in connection with the first aspect of theinvention, the above-mentioned invalid parameter may be also used toencode further information; e.g., a further parameter value. Provided aplurality of invalid values are available for the invalid parameter,then all invalid values are associated with the information that the DCIcarrying said invalid parameter is a DCI carrying one out of a pluralityof TDD configurations. On the other hand, each (or a group) of theinvalid values is associated with a different value of anotherparameter. Thus, further information can be transported to the mobilestation without using further bits. For example, the actual TDDconfiguration can be encoded into the invalid parameter; at least sevendifferent invalid parameter values need to be available to distinguishbetween the seven TDD configurations. Then, based on the particularinvalid parameter value used in the DCI, the mobile station candetermine the particular TDD configuration.

Instead of taking a known DCI Format (such as DCI Format 1C, defined by3GPP), it is also possible to define a new DCI Format exclusively forthe purpose of transporting the dynamic TDD re-configuration indication,and possibly further additional parameters as will be discussed later inmore detail.

According to a third aspect of the invention, the TDD configuration isdirectly encoded into the DCI, similar to the second aspect of theinvention. The DCI further comprises an invalid parameter, which allowsthe mobile station to detect that the received DCI is carrying a TDDconfiguration indication. Correspondingly, in case the mobile stationdetermines that the DCI comprises said particular invalid parameter, itwill proceed to determine the particular TDD configuration comprised inthe DCI.

For the third aspect of the invention, it is assumed that any of thevarious known DCI Formats defined by 3GPP can be used, such a DCI Format1C, already discussed for the first and second aspect of the invention.However, other formats may be used instead.

DCI Format 1C, as defined by 3GPP, conventionally includes a resourceblock assignment (RBA) parameter for the PDSCH assignment. For purposesof the third aspect, said RBA parameter may be set to an invalid value.

As with the previous aspects, further information may be encoded intosaid invalid parameter, provided a plurality of invalid values exist forthe invalid parameter. While any of the invalid values indicates thatthe DCI (carrying said invalid parameter) serves the purpose oftransporting the TDD configuration, each (or a group) of the invalidvalues is associated with further information. For example, the actualTDD configuration can be encoded into the invalid parameter; at leastseven different invalid parameter values need to be available todistinguish between the seven TDD configurations. Then, based on theparticular invalid parameter value used in the DCI, the mobile stationcan determine the particular TDD configuration.

A further improvement of the third aspect assumes that the errordetection code for the DCI is scrambled with a so called systeminformation identifier (SI-RNTI in 3GPP). The SI-RNTI is normally usedin the 3GPP systems to transport system information, and differentSI-windows are defined such that the mobile station can determine whichsystem information message can be indicated in which SI-window (c.f.3GPP TS 36.331, sections 5.2.1.2 and 5.2.3). According to 3GPP, only oneSI message can be transmitted per SI-window, but multiple times withinthat SI-window (if necessary). Since the different SI-messages can beconfigured with different periodicities, it is possible that certainSI-windows are not used for any SI-message; in other words, the mobilestation is aware that in such unused SI-windows no SI-messagetransmission will be performed by the base station. This mobile stationknowledge is taken advantage of by transmitting the DCI transporting theTDD configuration within such an unused SI-window, although the CRC forthe DCI is scrambled with the SI-RNTI. The reception within an unusedSI-window, allows the mobile station, in combination with the invalidparameter, to determine that the DCI is transporting a TDD configurationwith a higher certainty.

In a variant, a TDD-DCI reception window is defined, which is to beunderstood as restricting where the mobile station expects TDD-DCImessage to just particular subframes and/or radio frames. In otherwords, a preferably periodic pattern of subframes and/or radio frames isdefined as the TDD-DCI reception window, where the TDD configurationmessage can be transmitted by the base station, and/or only needs to bereceived and detected by the mobile station.

A first embodiment of the present invention provides a method forindicating one of a plurality of Time Division Duplex, TDD,configurations to a mobile station in a communication system. The TDDconfiguration defines uplink, downlink and special subframes within oneor more radio frames. The mobile station receives from a base station adownlink control information and a corresponding error detection codefor the downlink control information, wherein the error detection codeis scrambled by the base station with an identifier associated with aTDD configuration. Then, the mobile station determines the identifierused for scrambling the error detection code of the downlink controlinformation. The mobile station determines the TDD configuration fromthe identifier used for scrambling the error detection code of thedownlink control information.

A first embodiment of the present invention provides a mobile stationfor processing one of a plurality of Time Division Duplex, TDD,configurations in a communication system. The TDD configuration definesuplink, downlink and special subframes within one or more radio frames.A receiving section of the mobile station receives from a base station adownlink control information and a corresponding error detection codefor the downlink control information. The error detection code isscrambled by the base station with an identifier associated with a TDDconfiguration. A processor of the mobile station determines theidentifier used for scrambling the error detection code of the downlinkcontrol information. The processor of the mobile station furtherdetermines the TDD configuration from the identifier used for scramblingthe error detection code of the downlink control information.

A first embodiment of the present invention provides a base station forindicating one of a plurality of Time Division Duplex, TDD,configurations to a mobile station in a communication system. The TDDconfiguration defines uplink, downlink and special subframes within oneor more radio frames. A processor of the base station decides on a TDDconfiguration, and generates a downlink control information and acorresponding error detection code for the downlink control information.The processor further scrambles the generated error detection code withan identifier associated with the decided TDD configuration. Atransmitter transmits the generated downlink control information andscrambled error detection code to the mobile station.

A second embodiment of the present invention provides a method forindicating one of a plurality of Time Division Duplex, TDD,configurations to a mobile station for at least one target cell in acommunication system. The TDD configuration defines uplink, downlink andspecial subframes within one or more radio frames. The mobile stationreceives from a base station of a first cell a downlink controlinformation and a corresponding error detection code for the downlinkcontrol information. The error detection code for the downlink controlinformation is scrambled by the base station with a target cellidentifier associated with the at least one target cell for which theTDD configuration is to be applied. The mobile station determines theidentifier used for scrambling the error detection code of the downlinkcontrol information. The mobile also determines the TDD configurationfrom the downlink control information, in case the determined identifieris the target cell identifier, and determines the at least one targetcell to which to apply the determined TDD configuration from the targetcell identifier used for scrambling the error detection code of thedownlink control information.

A second embodiment of the present invention provides a mobile stationfor processing one of a plurality of Time Division Duplex, TDD,configurations in a communication system. The TDD configuration definesuplink, downlink and special subframes within one or more radio frames.A receiving section of the mobile station receives downlink controlinformation and a corresponding error detection code for the downlinkcontrol information. The error detection code for the downlink controlinformation is scrambled by the base station with a target cellidentifier associated with the at least one target cell for which theTDD configuration is to be applied. A processor of the mobile stationdetermines the identifier used for scrambling the error detection codeof the downlink control information. The processor determines the TDDconfiguration from the downlink control information, in case thedetermined identifier is the target cell identifier. The processordetermines the at least one target cell to which to apply the determinedTDD configuration from the target cell identifier used for scramblingthe error detection code of the downlink control information.

A second embodiment of the present invention provides a base station forindicating one of a plurality of Time Division Duplex, TDD,configurations to a mobile station in a communication system. The TDDconfiguration defines uplink, downlink and special subframes within oneor more radio frames. A processor of the base station decides on a TDDconfiguration. The processor generates a downlink control informationand a corresponding error detection code for the downlink controlinformation, the downlink control information indicating the decided TDDconfiguration. The processor scrambles the generated error detectioncode with a target cell identifier associated with the at least onetarget cell for which the TDD configuration is to be applied. Atransmitter transmits the generated downlink control information andscrambled error detection code to the mobile station.

A third embodiment of the present invention provides a method forindicating one of a plurality of Time Division Duplex, TDD,configurations to a mobile station in a communication system. The TDDconfiguration defines uplink, downlink and special subframes within oneor more radio frames. The mobile station receives from a base station adownlink control information, wherein the downlink control informationindicates the TDD configuration and further comprises an invalidparameter indicating that the downlink control information indicates oneof a plurality of TDD configurations. The mobile station determineswhether the received downlink control information comprises the invalidparameter. The mobile station determines the TDD configuration from thedownlink control information, in case the received downlink controlinformation comprises the invalid parameter.

A third embodiment of the present invention provides a mobile stationfor processing one of a plurality of Time Division Duplex, TDD,configurations in a communication system. The TDD configuration definesuplink, downlink and special subframes within one or more radio frames.A receiving section of the mobile station receives from a base station adownlink control information, wherein the downlink control informationindicates the TDD configuration and further comprises an invalidparameter indicating that the downlink control information indicates oneof a plurality of TDD configurations. A processor of the mobile stationdetermines whether the received downlink control information comprisesthe invalid parameter. The processor further determines the TDDconfiguration from the downlink control information, in case thereceived downlink control information comprises the invalid parameter.

A third embodiment of the present invention provides a base station forindicating one of a plurality of Time Division Duplex, TDD,configurations to a mobile station in a communication system, the TDDconfiguration defining uplink, downlink and special subframes within oneor more radio frames. A processor of the base station decides on a TDDconfiguration. The processor generates a downlink control informationand a corresponding error detection code for the downlink controlinformation, the downlink control information indicating the decided TDDconfiguration and comprising an invalid parameter indicating that thedownlink control information indicates one of a plurality of TDDconfigurations. A transmitter of the base station transmits thegenerated downlink control information to the mobile station.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the following the invention is described in more detail withreference to the attached figures and drawings.

FIG. 1 shows an exemplary architecture of a 3GPP LTE system,

FIG. 2 shows an exemplary overview of the overall E-UTRAN architectureof 3GPP LTE,

FIG. 3 shows exemplary subframe boundaries on a downlink componentcarrier as defined for 3GPP LTE (Release 8/9),

FIG. 4 shows an exemplary downlink resource grid of a downlink slot asdefined for 3GPP LTE (Release 8/9),

FIG. 5 exemplifies the processing structure for one downlink controlinformation as defined by 3GPP,

FIG. 6 shows the seven currently-standardized TDD UL/DL configurations0-6, the respective definitions of the 10 subframes and theirswitch-point periodicity,

FIG. 7 illustrates the structure of a radio frame, being composed of twohalf-frames and 10 subframes, for a 5 ms switch-point periodicity,

FIG. 8 shows the seven currently-standardized TDD UL/DL configurations0-6, of FIG. 6, and an exemplary association with seven TDD-RNTIsaccording to a first embodiment,

FIG. 9 illustrates a basic flow diagram for the functioning of themobile station according to a first embodiment of the invention,

FIG. 10 shows the seven currently-standardized TDD UL/DL configurations0-6, of FIG. 6, and an exemplary association with seven TDDconfiguration indication values according to a second and thirdembodiment,

FIG. 11 schematically illustrates a scenario with many small cells andone macro cell, termed enhanced Local Area,

FIG. 12 illustrates a basic flow diagram for the functioning of themobile station according to the second embodiment,

FIG. 13 illustrates a basic flow diagram for the functioning of themobile station according to the third embodiment, and

FIG. 14 shows two radio frames with different TDD UL/DL configurations,together with some timing relations for data and feedback transmissions.

DETAILED DESCRIPTION

The following paragraphs will describe various embodiments of theinvention. For exemplary purposes only, most of the embodiments areoutlined in relation to a radio access scheme according to 3GPP LTE(Release 8/9) and LTE-A (Release 10/11/12) mobile communication systems,partly discussed in the Technical Background section above. It should benoted that the invention may be advantageously used for example in amobile communication system such as 3GPP LTE-A (Release 10/11/12)communication systems as described in the Technical Background sectionabove, but the invention is not limited to its use in this particularexemplary communication networks.

The term “TOD configuration” refers to the TDD uplink/downlinkconfiguration as defined in the current standard, where the TDDconfiguration defines for each subframe of a radio frame whether same isa downlink, uplink or special subframe. The term “TDD configurationindex” is a number (currently 0-6) respectively associated with one outof the seven possible TDD UL/DL configurations, and is defined in thetechnical standards of 3GPP (see FIG. 6).

The term “default TDD configuration” used in the claims and alsothroughout the description refers to the TDD configuration that issemi-statically configured in the system by using the SIB1 as explainedin the background section. Put differently, the default TDDconfiguration is that one TDD configuration broadcast to all UEs in thecommunication area of the base station using the conventional mechanismof the system information acquisition and change procedure. Of course,the “default TDD configuration” can also be changed duringcommunication, albeit not as dynamically as with the current invention,but with a long time cycle.

The term “scrambling” used in the claims in connection with the errordetection code and used in the detailed description mainly in connectionwith a CRC (as an example of the error detection code) refers to theprocess of implicitly encoding, e.g., an identifier into the errordetection code (CRC). The term “masking” is assumed equivalent in thisapplication.

The term “invalid parameter” used in the claims and the descriptionshall be broadly understood as a parameter having an invalid value, thusconstituting an invalid parameter.

In the following, several embodiments of the invention will be explainedin detail. The explanations should not be understood as limiting theinvention, but as mere examples of the invention's embodiments to betterunderstand the invention. A skilled person should be aware that thegeneral principles of the invention as laid out in the claims can beapplied to different scenarios and in ways that are not explicitlydescribed herein. Correspondingly, the following scenarios assumed forexplanatory purposes of the various embodiments shall not limit theinvention as such.

The various embodiments explained for the invention in general refer toTDD configurations and in particular introduce a fast mechanism fordynamically changing the TDD configuration from the default TDDconfiguration (configured through SIB) to a target TDD configuration.

As explained in the background section, the semi-static re-configurationof the TDD configuration of the prior art is slow and cumbersome andshall be enhanced by a dynamic process according to one of the variousembodiments explained below.

The three following embodiments use the transmission of a DCI from abase station to indicate a change of the TDD configuration for one ormore cells. The TDD configuration may be either implicitly encoded intosaid transmission (in the CRC, as for the first embodiment) or in a moredirect way as a parameter of the DCI part (as for the second and thirdembodiment), or is encoded in a transport block that is indicated by theDCI.

First Embodiment

According to a first set of embodiments of the invention, the TDDconfiguration is encoded into the CRC of a DCI, both transmitted(usually broadcast) from the base station for a particular radio cell.

To said end, seven different RNTIs are defined, e.g., at the basestation or another network entity, each of the seven different RNTIsbeing associated with one of the seven TDD configurations, such thatevery TDD configuration 0-6 is associated with one different RNTI. FIG.8 illustrates a possible association, where TDD_0-6_RNTIs are associatedwith the TDD configurations. The RNTI cost is thus strictly limited bythe number of TDD configurations, and for instance not related to thenumber of small cells in the eLA scenario (see later, secondembodiment). The TDD RNTIs are preferably 16-24 bit long and can befreely selected, but are preferably chosen from the range FFEO-FFFC inhexadecimal notation for the 16-bit case, and can be specified in asimilar fashion as currently the M-RNTI, P-RNTI, SI-RNTI, or determinedand configured by the base station and conveyed to mobile receivers bymeans of RRC configuration messages or system information transmission.

In one variation of the first embodiment (which also applies to thesecond and third embodiment), not all of the seven TDD configurationsneed to be associated. In that case, there is no need for sevendifferent RNTIs, but, e.g., four TDD-RNTIs suffice to distinguishbetween the necessary TDD configurations that shall be available for thedynamic TDD re-configuration according to the invention.

The TDD-RNTI—TDD-configuration associations can be specified in asimilar fashion as currently the M-RNTI, P-RNTI, SI-RNTI, or determinedand configured by the base station and conveyed to the mobilestation(s); and possibly to the base station(s), in case a differentnetwork entity takes the decision. This may be done in various differentways, and the particular way used is not important for the functioningof the invention. For example, the association of the table in FIG. 8can be transmitted using RRC messages, system information messages, ormay be done during connection establishment. Correspondingly, both thebase station and the mobile station have the information necessary toimplement the dynamic TDD re-configuration according to the firstembodiment.

The base station at a certain point in time may decide that the defaultTDD configuration is not optimal, and that another TDD configurationwould be more beneficial. This may, e.g., due to a different trafficsituation or similar circumstances. The base station thus decides on atarget TDD configuration (among the available remaining six TDDconfigurations), different from the default TDD configuration, andperforms the dynamic TDD re-configuration as follows.

The base station after deciding on the new TDD configuration for aparticular cell(s), generates a DCI (new, or of a known format, or of aknown format but as an extension thereto, see below) and then calculatesan error detection code (in 3GPP, a CRC is used as error detection code)for the generated DCI. In the prior art the CRC would be scrambled withany of the various RNTIs, depending on the kind of DCI that istransmitted. In this particular case, the CRC, calculated for the DCI,is scrambled with the TDD-RNTI associated with the decided target TDDconfiguration, e.g., with TDD_1_RNTI for TDD configuration 1 (see FIG.8; and provided that the default TDD configuration is not TDD config 1).The actual scrambling of the CRC and TDD RNTI can be performed in theusual manner, as commonly known in the technical field and explained inthe background section as an example for 3GPP LTE.

After the base station generated the DCI, calculated the CRC andscrambled the CRC with the corresponding TDD RNTI, the DCI and scrambledCRC are transmitted in the cell. The DCI/CRC message can be transmittedin the PDCCH or the ePDCCH, and preferably in the common search spacethereof in case many or all mobile stations should be informed of there-configuration. In other cases, a transmission in the UE specificsearch space can be more efficient because the transmission parameterscan be tailored to the intended recipient and the respective prevailingtransmission conditions.

According to one variant of the embodiment, one of the already availabledownlink control information messages as defined by 3GPP, and brieflydiscussed in the background section, is reused for said purpose. Inother words, the base station reuses one of the DCI Formats 0, 1, 1A,1B, 1C, 1D, 2, 2A, 2B, 2C, 2D, 3, 3A, 4 (as defined at the time offiling this application; or any other format defined by 3GPP in thefuture) for the dynamic TDD re-configuration instead of for the actuallyintended purpose of the particular DCI format message.

For instance, the DCI Format 1C message can be re-used, the Format 1Chaving the least number of bits out of all the available DCI formats. Itshould be noted that though in the following description also for thesecond and the third embodiments mainly the DCI format 1C is used forillustrating the invention's principles, other DCI formats may bere-used for the purposes of the invention.

The DCI Format 1C is defined in 3GPP to include the following fields:

resource block assignment (RBA) 3-9 bits (bandwidth dependent)Modulation and coding scheme (MCS) 5 bits Gap Value indication 1 bits(only if bandwidth >= 50 PRB)

A more detailed discussion on the DCI Format 1C content can be found in3GPP TS 36.212 Chapter 5.3.3.1.4, incorporated hereby by reference.Thus, the DCI format 1C message can be between 8 and 15 bits long.

Correspondingly, instead of sending the above parameters for the PDSCHassignment as intended for the DCI Format 1C, the base station mayinclude other parameters into the DCI. This partly depends on thebandwidth in the cell, since the amount of bits available in the DCIFormat 1C depends on the bandwidth. These other parameters to beincluded in the DCI Format 1C may comprise at least one of thefollowing:

-   -   a target cell identifier, identifying the target cell for which        the TDD configuration as implicitly encoded into the CRC of the        DCI shall be applied,    -   a HARQ instruction, for instructing the mobile station(s) to        reset or not reset the HARQ protocol upon applying the new TDD        configuration,    -   a lifetime parameter for the encoded TDD configuration,        indicating to the mobile station(s) the amount of time said TDD        configuration shall be applied, before switching back to the        default TDD configuration,    -   a padding field with a pre-defined bit value (virtual CRC),        which can be used to “fill” the DCI, such that the remaining,        otherwise unused bits, are put to good use so as to lower the        false alarm risk    -   a buffer status report (BSR) procedure instruction, instructing        to cancel a pending BSR procedure or to trigger a new BSR        procedure, upon applying the indicated TDD configuration,    -   a scheduling request (SR) procedure instruction, instructing to        cancel a pending SR procedure or to trigger a new SR procedure,        upon applying the indicated TDD configuration,    -   a random access channel (RACH) procedure instruction,        instructing to cancel a pending RACH procedure or to trigger a        new RACH procedure, upon applying the indicated TDD        configuration,    -   a power headroom reporting (PHR) instruction, instructing to        cancel a pending PHR or to trigger a new PHR, upon applying the        indicated TDD configuration.

These parameters are only briefly discussed above for illustrationpurposes and will be explained in more detail later.

When using such a known DCI format, it is also possible for the basestation to set one of the parameters defined for said known DCI formatto an invalid value and to thus use the invalid parameter as an “escapecodepoint” for indicating to the mobile station that the DCI carryingthe invalid parameter is not conventional but carries a TDD UL/DLconfiguration indication. The DCI message thus includes said particular(invalid) parameter, as a conventional DCI message, however with aninvalid value. This invalid value is known to both the base station andthe mobile station. Assuming as an example the already standardized DCIformat 1C, the resource block assignment parameter can be set to aninvalid value, such as all bit values being “1”.

An invalid value for a parameter or a parameter combination can begenerally characterized as representing a state that is reserved orcontradicts requirements on the indicated parameter. For example, aninvalid resource block assignment value is one that would result in theassignment of at least one resource block with a negative index or of atleast one resource block outside of the available resource blocks.Another invalid value example refers to a HARQ process number parameterin case of TDD with a HARQ index that indicates a HARQ process beyondthe defined maximum number of HARQ processes as specified in 3GPP TS36.213 Table 7-1. An example of an invalid parameter combination where avalue is representing a reserved state is the ‘Precoding information’ asavailable, e.g., in DCI format 2, where depending on the number ofindicated transport blocks, different precoding information values aredefined as ‘reserved’, and where the number of indicated transportblocks depends on the combination of the indicated modulation and codingscheme and redundancy version, as specified in 3GPP TS 36.213 chapter7.1.7.2.

For resource allocation type 2, at least one RBA state is invalid forall downlink bandwidths 6-110 PRBs, namely when all bit values are setto “1”. For 10 and 13 PRBs, there is exactly one invalid state, thealready mentioned all bits=1. For 6 PRBs, there are 2 invalid RBAvalues. For 15 PRBs, there are 4 invalid RBA values. For 25 PRBs, thereare 50 invalid RBA values. For 50 PRBs, there are 62 invalid RBA valuesfor gap 1, and 83 invalid RBA values for gap 2. For 75 PRBs, there are120 invalid RBA values, and for 100 and 110 PRBs, there are 212 invalidRBA values.

Especially, when having a bandwidth where there are more than oneinvalid values (i.e., all but for 10 and 13 PRBs, which are however oflower importance in practice), additional information could be encodedinto this invalid parameter of the DCI, besides the indication that theDCI carrying the invalid parameter carries a TDD UL/DL configurationindication. The additional information may be one of the above-mentionedother parameters, namely at least one of a target cell identifier, aHARQ instruction and a lifetime parameter, BRS instruction, SRinstruction, RACH instruction and PHR instruction. Of course, if one ofthese parameters is encoded into the invalid parameter, then, the DCIdoes not need to include said particular parameter separately in itspayload.

For example, taking the bandwidth of 15 PRB, with the 4 invalid RBAvalues, all of the 4 invalid RBA values indicate to the mobile stationthat the DCI carrying said invalid RBA value, includes an indication asto the dynamic TDD configuration. Further, each particular invalid RBAvalue might be further associated with one different lifetime parameter(e.g., 10 ms, 40 ms, 100 ms and 200 ms), or distinguish betweendifferent target cells for which the TDD configuration shall apply(e.g., PCell, SCell1, SCell2 or SCell3).

Alternatively, 2 of the invalid RBA values are associated with thereset-HARQ instruction and the other 2 invalid RBA values are associatedwith the do-no-reset-HARQ instruction. Similar considerations apply forthe other bandwidths; e.g., when only 2 invalid states are available forthe RBA parameter, then, only two different states of the additionalinformation can be encoded, such as the HARQ instruction, or thelifetime parameter (e.g., distinguishing between the valid periods of 10ms and 40 ms).

As an alternative to reusing a known DCI format (such as Format 1C), itis also possible to make an extension to the known DCI format, such thatthe known DCI format is used only for particular cases, and another“version” of the known DCI format is used for other particular cases.For instance, it would be possible to adapt a known DCI format (such asFormat 1C) to be only applicable for particular radio frames orsubframes within particular radio frames, and to include a definitionthat defines the known DCI format to be used for dynamic TDD UL/DLre-configuration for other radio frames or other subframes withinparticular radio frames, where depending on the “version”, the DCIformat may contain different information elements.

Alternatively to the above, it is also possible to use a DCI formatspecifically defined for the purpose of dynamic TDD re-configuration;e.g., also being of a different size than the already-defined DCIformats. In said case, the amount of bits of the DCI does not depend onthe cell bandwidth, but can be defined freely depending on theparameters that are to be transmitted in this new DCI. For example, aDCI Format 1E can be defined that includes at least one of theabove-listed parameters (target cell identifier, HARQ instruction,lifetime parameter, padding field, BSR instruction, SR instruction, RACHinstruction, PHR instruction).

In summary, the base station transmits the DCI and scrambled CRC in hiscell, and the mobile station(s) in the cell receive the DCI andscrambled CRC. The processing of the DCI and CRC according to this firstembodiment is explained in connection with FIG. 9, which shows a flowdiagram of the mobile station for a basic first embodiment of theinvention.

The mobile station listens on the PDCCH and EPDCCH to detect DCImessages, intended for the mobile station. After receiving the DCI andCRC from the base station, the mobile station proceeds to determine theRNTI with which the CRC was scrambled. The particular error detectioncheck and descrambling may be performed in the usual manner, asdiscussed exemplary in the background section for 3GPP LTE. For example,the mobile station performs an error detection check for the DCI, basedon the CRC, the DCI and various possible candidate identifiers that mayhave been used to scramble the DCI, amongst these the seven TDD RNTIs.For only one of the RNTIs, the CRC check performed by the mobile stationis successful. Thus, the mobile station determines that the particularone TDD RNTI was used for scrambling.

The mobile station then proceeds to determine with which TDDconfiguration the determined TDD RNTI is associated by, e.g.,referencing the table as defined in FIG. 8. Thus, for example the mobilestation determines it shall switch to the TDD configuration 1, insteadof continuing to use the default TDD configuration.

The thus determined TDD configuration is then applied by the mobilestation for a particular time. This may be either pre-defined to be afixed amount of time, such as 1, 2 or 4 radio frames. Alternatively, thetime can be dynamically indicated, e.g., by using the lifetime parameteralready mentioned before as (optionally) being part of the DCI payloador being encoded into the invalid parameter (see above). Assuming thatthe mobile station receives the DCI/CRC transmission in radio frame n,it then correspondingly processes the DCI and CRC, and applies theindicated TDD configuration for a particular number of radio frames n+1,n+2, n+3 etc., depending on the lifetime parameter in the DCI or thepre-defined fixed amount of time. After the dynamically indicated TDDconfiguration “expires”, i.e., shall no longer be applied, the mobilestation switches back to the default TDD configuration until for exampleit receives another TDD DCI for dynamic TDD UL/DL re-configuration.

Alternatively, the mobile station can also proceed to apply the new TDDconfiguration until it receives another TDD re-configuration; in otherwords, the new TDD configuration is not specified for a particularamount of time but indefinitely until instructed otherwise.

The mobile station may also determine further parameters from the DCI,depending on whether the DCI includes same. For instance, the mobilestation may determine the target cell, the HARQ instruction, lifetimeparameter, padding field value, BRS instruction, SR instruction, RACHinstruction and/or PHR instruction therefrom.

Details as to how the information gained from these additionalparameters is used, is explained later separately in connection withthese parameters.

According to a further variant of the first embodiment, the CRC of theDCI is scrambled by a TDD-RNTI, although only one TDD-RNTI would berequired to be defined for this purpose instead of multiple TDD-RNTIs,where the DCI assigns physical resources for transmission of a transportblock, in a similar fashion as, e.g., currently DCI format 1A can beused to assign physical resources for a transport block. Said transportblock can then represent a MAC or RRC message, which containsinformation and parameters about the TDD (re-)configuration as, e.g.,outlined in the later sections of the present application. In otherwords, instead of (or in addition to) using the DCI payload to indicateone or more TDD configuration parameters, the RNTI is used to identifythat a reconfiguration message is transmitted, and the DCI payload givesinformation about the transport block that carries the TDD configurationparameter(s).

Second Embodiment

The second embodiment of the invention mainly differs from the firstembodiment explained above in that the TDD UL/DL configuration is notencoded into the RNTI used for scrambling the CRC of the DCI, butinstead a TDD UL/DL configuration indication is included into the DCIpayload. Most of the remaining details however remain the same betweenthe first and second embodiments.

The TDD UL/DL configuration indication in the DCI distinguishes betweenthe 7 different TDD UL/DL configurations of FIG. 6; thus, a 3-bit fieldsuffices to indicate the particular TDD UL/DL configurations, where eachindication value is associated with one of the TDD configurations.Again, it is also possible to distinguish between less TDD UL/DLconfigurations, such that already a 2-bit (or even a 1-bit) fieldsuffices; however, with the disadvantage that the dynamic TDDre-configuration is not so flexible.

The association between the 3-bit values and the TDD configurations canbe defined by the base station or another network entity. An exemplaryassociation for all seven TDD configurations using a 3-bit TDDindication field is illustrated in FIG. 10. Information on theassociations between the TDD configuration indication values and theactual TDD configurations is informed to the mobile station; andpossibly to the base station(s), in case a different network entitytakes the decision. As with the first embodiment, the informingprocedure may be done in various different ways; e.g., using RRCmessages, system information messages, or may be done during connectionestablishment. Correspondingly, both the base station and the mobilestation have the necessary information to implement the dynamic TDDre-configuration of the invention.

As for the first embodiment, the base station decides to change the TDDUL/DL configuration from the default TDD configuration to another targetTDD configuration, e.g., for the reason that the target TDDconfiguration is better suited for the current traffic. The base stationthus wants to perform a dynamic TDD re-configuration and generates a DCIincluding the above-mentioned TDD UL/DL configuration indication.

The base station thus generates a DCI for the dynamic TDDre-configuration, wherein the DCI includes the TDD configurationindication, indicating the TDD configuration which the base stationdecided. Also as already explained for the first embodiment in detail,the DCI may include further parameters, such as at least one of the HARQinstruction, the lifetime parameter, the padding field, BRS instruction,SR instruction, RACH instruction and PHR instruction.

In the same way as for the first embodiment, the DCI generated by thebase station, can be one of the already available downlink controlinformation messages as defined by 3GPP (e.g., the DCI Formats 0, 1, 1A,1B, 1C, 1D, 2, 2A, 2B, 2C, 2D, 3, 3A, 4). In this case, instead ofsending the usual parameters of the defined DCI Format (such as RBA,MCS, Gap value Indication for Format 1C), the base station includesother parameters. As explained above, the TDD configuration indicationfield is included.

When using a known DCI format, it is also possible for the base stationto set one of the parameters defined for said known DCI to an invalidvalue. The invalid parameter indicates the mobile station that the DCIcarrying the invalid parameter, further carrier a TDD UL/DLconfiguration indication. This has been explained in detail for thefirst embodiment, and the same principles apply to the second embodimenttoo, and are not repeated for sake of conciseness. Instead, the readeris kindly pointed to the corresponding passages of the first embodiment.

Furthermore, the invalid parameter may not only be understood asindicating to the mobile station that the DCI carries a TDD UL/DLre-configuration indication, but this invalid parameter may encode afurther parameter, such as the particular TDD UL/DL re-configurationindication, or any of the other parameters mentioned above: HARQinstruction, lifetime parameter, BRS instruction, SR instruction, RACHinstruction, PHR instruction. This is very similar to the use of theinvalid parameter for the first embodiment, except that the invalidparameter for the first embodiment may encode the target cellidentifier, but not the TDD configuration indication, whereas this isthe other way round for the second embodiment.

Alternatively to reusing a known DCI format (such as format 1C), it isalso possible to make an extension to the known format, as alreadyexplained for the first embodiment. To avoid repetition, the reader isreferred to the corresponding sections of the first embodiment.

As a further alternative, it is also possible to use a DCI formatspecifically defined for the purpose of dynamic TDD re-configuration,e.g., with a different size. Again, the reader is referred to thecorresponding sections of the first embodiment.

Independently from the actually used DCI format and independently fromwhether the DCI includes or not further parameters, the base stationcalculates an error detection code for the thus generated DCI. Accordingto the second embodiment, the error detection code (CRC) is thenscrambled with a cell identifier, identifying the target cell(s) forwhich the dynamic TDD re-configuration is to be applied. The cellidentifier can also be termed SC-RNTI, Small Cell-RNTI.

Since the cell identifier for scrambling with the CRC is assumed to havethe same length as the CRC, i.e., is expected to be 16-24 bit long, itis particularly suitable to distinguish between many different cells andthus can preferably be used in scenarios where there are a lot of cells.The 16-24 bit cell identifier values can be flexibly associated witheither single cells or different group of cells. This has the advantagethat the base station can flexibly perform the TDD re-configuration foreither single cells (e.g., SCell1) and/or group of cells (e.g.,neighboring cells, SCell1-SCell10) by using the particular target cellidentifier value associated therewith. Also, one of the available targetcell identifiers may also identify all cells as target cells. Theassociation between the target cell identifier values and the targetcell (groups) can be decided in the base station, or another networkentity, and then should be informed to the mobile station (and the basestation), such that both the base station and the mobile station havethe same information necessary for the dynamic TDD re-configurationaccording to the second embodiment. As for the first embodiment, it isnot possible to use all of the available RNTI values (65536 differentvalues are available for the case of a 16-bit RNTI), since some of themare already reserved for other purposes. Alternatively, the associationsmay be pre-defined and fixed by the standard.

Current mechanisms, such as carrier indication fields, only support 8different cells at most. LTE-Advanced however shall support enhancedLocal Area (eLA), where many tens of small cells could be withincoverage of a macro cell. This is schematically illustrated in FIG. 11,where a large-coverage macro cell is operated around 800 MHz, and withinmany small-coverage cells are operated around 3.4 GHz. In such a celldeployment, it may be necessary for a mobile station to differentiatebetween more than 7 small cells especially if the mobile station ismoving through the coverage area of the macro cell and should performradio measurements on a multitude of small cells to determine the onewith the most favorable radio conditions

In summary, the base station transmits the DCI and scrambled CRC for theDCI, and the mobile stations located in the cell receive the DCI andscrambled CRC. The processing of the DCI and CRC in the mobile stationaccording to the second embodiment is explained with reference to FIG.12.

The mobile station listens on the PDCCH and EPDCCH to detect DCImessages, intended for the mobile station. Thus, the mobile stationreceives the DCI and CRC from the base station, and determines the RNTIwith which the CRC was scrambled. The particular error detection checkand descrambling may be performed in the usual manner, as discussedexemplary in the background section for 3GPP LTE. For example, themobile station performs an error detection check for the DCI, based onthe CRC, the DCI and various possible candidate identifiers that mayhave been used to scramble the DCI, amongst these the target cellidentifiers. For only one of the RNTIs, the CRC check performed by themobile station is successful. Thus, the mobile station determines thatone of the particular target cell identifiers was used for scrambling.

From the fact that a target cell identifier was used for scrambling theCRC, the mobile station can already deduce that the DCI furtherindicates a TDD configuration for performing a dynamic TDDre-configuration. Correspondingly, the mobile station then proceeds todetermine the particular TDD configuration encoded into the DCI in oneof the different ways as explained above. Thus, the mobile station mayeither read an actual TDD configuration indication field value, as shownin FIG. 10, and associate the value with a corresponding TDDconfiguration; or, the mobile station determines an invalid parametervalue, and determines from the invalid parameter value the associatedTDD configuration.

Furthermore, the mobile station determines from the determined targetcell identifier, the particular target cell, or group of cells, forwhich the encoded TDD configuration is intended and shall be applied.The TDD re-configuration is only to be applied by a mobile station, ifthe mobile station is actually belonging to the identified target cell.Otherwise, the TDD re-configuration can be ignored by the mobilestation.

If included in the DCI, the mobile station may determine the furtherparameters from the DCI payload, e.g., the lifetime parameter, the HARQinstruction, padding field value, BRS instruction, SR instruction, RACHinstruction and/or PHR instruction. Details as to how the informationgained from these additional parameters is used, is explained laterseparately in connection with these parameters.

The thus determined TDD configuration is then applied by the mobilestation for a particular time. As with the first embodiment, this may beeither pre-defined to be a fixed amount of time, such as 1, 2 or 4 radioframes. Alternatively, the time can be dynamically indicated, e.g., byusing the lifetime parameter already mentioned before as being(optionally) part of the DCI payload or being encoded into the invalidparameter (see above). Assuming that the mobile station receives theDCI/CRC transmission in radio frame n, it then correspondingly processesthe DCI and CRC, and applies the indicated TDD configuration for aparticular number of radio frames n+1, n+2, n+3 etc., depending on thelifetime parameter in the DCI or the pre-defined fixed amount of time.After the dynamically indicated TDD configuration “expires”, i.e., shallno longer be applied, the mobile station switches back to the defaultTDD configuration until for example it receives another TDD DCI fordynamic TDD UL/DL re-configuration.

Alternatively, the mobile station can also proceed to apply the new TDDconfiguration until it receives another TDD re-configuration; in otherwords, the new TDD configuration is not specified for a particularamount of time but indefinitely until instructed otherwise.

According to a variant of the second embodiment, the CRC of the DCI isscrambled by an SC-RNTI, and the DCI assigns physical resources fortransmission of a transport block, in a similar fashion as, e.g.,currently DCI format 1A can be used to assign physical resources for atransport block. Said transport block can then represent a MAC or RRCmessage, which contains information and parameters about the TDD (re-)configuration as, e.g., the desired TDD configuration, or the targetcell index, or other parameters outlined in the later sections of thepresent application.

Third Embodiment

The third embodiment of the invention is similar to the first and secondembodiment in that it deals with dynamic TDD UL/DL re-configurationusing the transmission of a DCI/CRC. Further, similar to the secondembodiment, the TDD UL/DL configuration is not implicitly encoded intothe RNTI, used for scrambling the CRC, but instead is included in theDCI payload. However, according to the third embodiment a target cellidentifier (SC-RNTI) is not used for scrambling the CRC of the DCI.However, the DCI includes an invalid parameter to indicate to the mobilestation that the DCI further includes an indication as to a TDDconfiguration. In other words, the invalid parameter already discussedin connection with the first and second embodiments as being an optionalparameter of the DCI, is for the third embodiment always included in theDCI payload.

Otherwise, many details already discussed for the first and secondembodiments remain the same for the third embodiment. For said reason,repetitions are avoided where possible, and the reader is referred tothe corresponding passages of the first and/or second embodiment.

In the same way as for the second embodiment, the TDD UL/DLconfiguration indication in the DCI distinguishes between all the 7different TDD UL/DL configurations of FIG. 6; or alternatively, maydistinguish between less TDD UL/DL configurations. Correspondingly, aTDD UL/DL configuration indication can be defined as exemplary depictedin FIG. 10. To avoid repetition, the reader is referred to the sectionsof the second embodiment explaining in detail the TDD UL/DLconfiguration indication; which may be included as a separate parameterin the DCI payload, or may be encoded into the invalid parameter whenenough invalid values are available as explained before. In any case,the base station and mobile station shall have a common understanding onhow the different TDD configurations may be indicated using the DCI.

As already discussed for the first and second embodiments, the basestation at a certain time may decide to change the TDD UL/DLconfiguration from the default TDD configuration to another TDD UL/DLconfiguration, e.g., for the reason that the TDD configuration is bettersuited for the current traffic. The base station thus wants to perform adynamic TDD re-configuration as will be explained below in connectionwith the third embodiment.

The base station generates a DCI, wherein the DCI includes the TDDconfiguration indication, for indicating the TDD configuration which thebase station decided. As explained for the first and second embodimentsin detail, the DCI may optionally include further parameters; for thisparticular third embodiment: the target cell identifier, the HARQinstruction, the lifetime parameter, the padding field, BRS instruction,SR instruction, RACH instruction and/or PHR instruction.

Since the DCI according to the third embodiment always includes theinvalid parameter, the DCI generated by the base station should be oneof the already-available downlink control information messages asdefined by 3GPP (e.g., the DCI Formats 0, 1, 1A, 1B, 1C, 1D, 2, 2A, 2B,2C, 2D, 3, 3A, 4). This already defined DCI message is then re-used forthe purpose of carrying the TDD indication configuration.

Furthermore, for the case where there are several invalid valuesavailable for the invalid parameter (especially for larger bandwidths),then it is possible to encode at least one of the above-mentionedfurther parameters into the invalid parameter, in a similar manner asfor the first and second embodiment.

For example, assuming the case where the DCI Format 1C is used, havingthe least number of bits, the RBA parameter of DCI format 1C can be usedas the invalid parameter and can be set to an invalid value. Asexplained for the first embodiment in detail, the RBA parameter can takea different number of invalid values depending on the bandwidth used inthe cell. One invalid value is the same for all bandwidths, namely whereall bits of the RBA parameter are set to one. For most bandwidthshowever, the RBA parameter can take several invalid values; for 6 PRBs,there are 2 invalid RBA values; for 15 PRBs, there are 4 invalid RBAvalues; for 25 PRBs, there are 50 invalid RBA values; for 50 PRBs, thereare 62 invalid RBA values for gap 1, and 83 invalid RBA values for gap2; for 75 PRBs, there are 120 invalid RBA values, and for 100 and 110PRBs, there are 212 invalid RBA values.

Additional information could be encoded into this invalid parameter ofthe DCI, besides the indication that the DCI carrying the invalidparameter carries a TDD UL/DL configuration indication. The additionalinformation may be one of the above-mentioned other parameters, namelyat least one of a TDD configuration, target cell identifier, a HARQinstruction, a lifetime parameter, BRS instruction, SR instruction, RACHinstruction and PHR instruction. Of course, if one of the mentionedparameters is encoded into the invalid parameter, then, the DCI does notneed to include said particular parameter separately in its payload.

Therefore, in one variant of the third embodiment (and actually also ofthe second embodiment), the DCI format 1C for dynamic TDDre-configuration includes the RBA parameter set to an invalid value (butencoding the particular TDD configuration) and a padding field for theremaining bits, the padding field being set to a pre-defined value andserving as a virtual CRC.

The base station generates the DCI as explained above, and thencalculates an error detection code (CRC) for the thus generated DCI. TheCRC is scrambled by the base station with an RNTI; which RNTI is used isnot important for the functioning of the third embodiment, however it isadvantageous for the mobile station to limit the operation to only oneor a restricted RNTI value(s) in order to minimize the risk oferroneously detecting a successful DCI transmission due to transmissionerrors. An advantageous variant of the third embodiment, where theSI-RNTI is used for scrambling will be explained in detail furtherbelow.

The base station transmits the DCI and scrambled CRC for the DCI, andthe mobile station(s) located in the cell receive the DCI and scrambledCRC. The processing of the DCI and CRC by the mobile station accordingto the third embodiment is explained with reference to FIG. 13.

The mobile station listens on the PDCCH and EPDCCH to detect DCImessages, intended for the mobile station. Thus, the mobile stationreceives the DCI and CRC from the base station. The CRC is descrambledand the content of the DCI is processed.

The mobile station then determines whether the DCI comprises an invalidparameter, and in case it does, the mobile station deduces that the DCIis not a conventional DCI, but is used by the base station for thedynamic TDD re-configuration and thus indicates a particular TDDconfiguration. The mobile station then proceeds to determine theparticular TDD configuration encoded into the DCI in one of thedifferent ways as explained above. Namely, the mobile station may eitherread an actual TDD configuration field value, as shown in FIG. 10, andassociate the value with a corresponding configuration; or the mobilestation determines the invalid parameter value, and associates theparticular invalid parameter value with the corresponding TDDconfiguration.

Furthermore, depending on whether the DCI includes further parameters,the mobile station may determine the value of any other parameter in theDCI, such as the target cell(s), the lifetime, an HARQ instruction, BRSinstruction, SR instruction, RACH instruction and/or PHR instruction; bethe other parameter encoded into the invalid parameter or being presentas a separate parameter in the DCI payload

For example, the mobile station determines from the determined targetcell identifier, the particular target cell, or group of cells, forwhich the encoded TDD configuration is intended and shall be applied.The TDD re-configuration is only to be applied by a mobile station, ifthe mobile station is actually belonging to the identified target cell.Otherwise, the TDD re-configuration can be ignored by the mobilestation. Details as to how the information gained from these additionalparameters is used, is explained later separately in connection withthese parameters.

The thus determined TDD configuration is then applied by the mobilestation for a particular time. As with the first embodiment, this may beeither pre-defined to be a fixed amount of time, such as 1, 2 or 4 radioframes. Alternatively, the time can be dynamically indicated, e.g., byusing the lifetime parameter already mentioned before as being(optionally) part of the DCI payload or being encoded into the invalidparameter (see above). Assuming that the mobile station receives theDCI/CRC transmission in radio frame n, it then correspondingly processesthe DCI and CRC, and applies the indicated TDD configuration for aparticular number of radio frames n+1, n+2, n+3 etc., depending on thelifetime parameter in the DCI or the pre-defined fixed amount of time.After the dynamically indicated TDD configuration “expires”, i.e., shallno longer be applied, the mobile station switches back to the defaultTDD configuration until for example it receives another TDD DCI fordynamic TDD UL/DL re-configuration.

Alternatively, the mobile station can also proceed to apply the new TDDconfiguration until it receives another TDD re-configuration; in otherwords, the new TDD configuration is not specified for a particularamount of time but indefinitely until instructed otherwise.

One improved variant of the third embodiment refers to the CRC of theDCI being scrambled by the base station with a system information RNTI(SI-RNTI), and furthermore the TDD configuration DCI being transmittedin an SI reception window which normally should not have been used bythe base station to send system information. This will be explained indetail below.

In the prior art, the time domain scheduling of the MIB and SIB1messages is fixed with periodicities of 40 ms and 80 ms respectively.Each SI message is transmitted in a defined periodically-occurring timedomain window, while physical layer control signaling indicates in whichsubframes within this window the SI is actually scheduled. Thescheduling windows of the different SI messages (referred to asSI-windows or SI reception windows) are consecutive (i.e., there areneither overlaps nor gaps between them) and have a common length that isconfigurable. SI-windows can include subframes in which it is notpossible to transmit SI messages, such as subframes used for SIB1, andsubframes used for the uplink in TDD.

SI messages may have different periodicities. Consequently, in someclusters of SI-windows all the SI messages are scheduled while in otherclusters only the SI messages with shorter repetition periods aretransmitted. For one example, the cluster of SI-windows beginning atSystem Frame Number (SFN) 0 contains all the SI messages, and thecluster starting at another SFN may contain only the first SI message,depending on the periodicities previously defined. For a more detaileddiscussion on SI-windows, please refer to the technical standard or toLTE—The UMTS Long Term Evolution—From Theory to Practice, Edited byStefanie Sesia, Issam Toufik, Matthew Baker, Chapters 3.2.2 and 3.2.2.1,incorporated herein by reference.

As a result, depending on the particular periodicities (especially forlong repetition periods/cycles), there will be SI-windows in which no SIis transmitted, and thus these SI-windows will not be used by basestation to transmit system information. This can be taken advantage of.

In one variant of the third embodiment, the DCI, which CRC is scrambledwith the SI-RNTI, is transmitted by the base station in one of saidunused SI-windows. The mobile station knows in advance that thisparticular SI-window will not be used to transmit system information,since the mobile station is also aware of the periodicities of theSI-messages. Thus, when the mobile station receives a SI-message (i.e.,the TDD DCI, which CRC is scrambled with the SI-RNTI), the mobilestation knows that this can not be a conventional SI-message.Correspondingly, it is aware that this SI-message, received within anSI-window which normally should not have been used by the base stationto transmit an SI-message, must be a TDD configuration message.Furthermore, the mobile station can corroborate this by determiningwhether the DCI payload includes an invalid parameter.

In order to relieve the mobile station of the burden of detectingpossible SI-messages in SI-windows which normally would not be used bythe base station for transmitting SI-messages, a further variant of thethird embodiment defines a “TDD-DCI reception window”. The TDD-DCIreception window is to be understood as restricting where the mobilestation should expect TDD-DCI message to just particular subframesand/or radio frames. In other words, preferably a periodic patternof—possibly but not necessarily adjacent—subframes and/or radio framesis defined as the TDD-DCI reception window (or equivalently pattern),where the TDD-DCI message can be transmitted by the base station, and/oronly needs to be received and detected by the mobile station.

Such a window can be used in general with any of the describedembodiments and independently of the used SI-RNTI. For exemplarypurposes, the following describes the situation where the TDD-DCIreception window is used and the SI-RNTI is used to scramble the CRC ofthe DCI. As mentioned above, the UE can know that the detected DCI is aTDD DCI if the DCI is detected in an SI window that is unused forSI-message transmissions as a function of the configured SIperiodicities. Such unused SI windows may therefore be more or lessfrequently occurring. It can therefore be beneficial—in order to createmore possibilities of transmitting a TDD DCI—to define a TDD-DCIreception window. In case a subframe is part of a used SI-window as wellas part of the TDD-DCI reception window, preferably the mobile stationassociates a successfully detected DCI with the CRC scrambled by theSI-RNTI as being a TDD-DCI and not used for the purposes of indicatingan SI transmission. Alternatively, in such a situation the mobilestation interprets such a DCI as a TDD-DCI if an invalid parameterwithin the DCI is detected, and as a DCI for indicating an SItransmission otherwise.

According to a variant of the third embodiment, the CRC of the DCI isscrambled by a SI-RNTI. In case this is detected by the mobile stationin an unused SI-window and/or in a subframe designated as part of aTDD-DCI reception window, the mobile station is aware that the DCI isintended for a TDD configuration message. In this variant, the DCIassigns physical resources for transmission of a transport block, in asimilar fashion as, e.g., currently DCI format 1A can be used to assignphysical resources for a transport block. Said transport block can thenrepresent a MAC or RRC message, which contains information andparameters about the TDD (re-)configuration as, e.g., the TDDconfiguration index or further parameters outlined in the later sectionsof the present application. Therefore, instead of (or in addition to)the TDD indication within the DCI message, the transport block indicatedby the DCI message contains the TDD indication.

Further Parameters

The above described first, second and third embodiments mention thatfurther parameters may be included in the downlink control informationused for the dynamic TDD UL/DL re-configuration, either as separateparameters of the DCI or encoded into the invalid parameter. Theseparameters were only briefly discussed and will be explained in moredetail below.

Target Cell Identifier

As already apparent from the term, this identifier shall identify theparticular cell for which the TDD UL/DL configuration, transmitted withthe DCI/CRC, shall apply. However, this parameter should be the one usedin the DCI, and may be different from the one used for scrambling theCRC of the DCI, as explained for the second embodiment. For instance,while the SC-RNTI used for scrambling is 16 bit, the target cellidentifier to be included into the DCI payload can any suitable size.

There may be scenarios in which one cell transmits the dynamic TDD UL/DLre-configuration message, although the TDD UL/DL re-configuration shallbe applied in another cell. This may be the case for the above mentionedenhanced local area (eLA) scenario. Particularly, when the TDDconfiguration is intended for an SCell, then preferably the dynamic TDDre-configuration may be transmitted in the PCell.

Depending on the number of different cells in the system, only a fewbits are necessary for the target cell identifier to distinguish betweenthe various cells.

The target cell identifier can be implemented in different ways. Forexample, the physical cell identity (PCID, in TS 36.211; PhysCellId inTS 36.331) defined by 3GPP Release 8 can be used, the PCID directlypointing to an index. Alternatively, the numbering currently used forSCell addition and modification (parameters SCellIndex,sCellToAddModList, SCellToAddMod-r10, see, e.g., TS 36.331, section5.3.10.3b and other sections therein) can be directly used, or a newrelation between target cell identifier and target cell can beestablished.

Another way of implementing the target cell identifier refers to the useof a 3-bit carrier indicator field (CIF). The CIF field is usuallyintended for cross-carrier scheduling, and identifies the carrier forwhich the scheduling refers. The CIF thus can identify another carrier,and thus allows the mobile station to determine for which cell (carrier)the TDD configuration received with the DCI is to be applied. Thispreferably reuses the numbering and relations similar to the procedureof SCell addition and modification (TS 36.331, section 5.3.10.3b andparameters SCellIndex, sCellToAddModList, SCellToAddMod-r10, describedin other sections therein)

Still another option for the target cell identifier is similar to theCooperative Multipoint (CoMP) method of 3GPP Release 10. Instead ofpointing to a physical cell identifier, the target cell identifier ispointing to one or more reference symbol resources or configurationssuch as CRS port or CSI-RS resource, resource as specified in TS 36.211,section 6.10.1 and 6.10.5, and as specified in information elementCSI-RS-Config in TS 36.311.

Still another option for the target cell identifier is to establish anew relation between target cell identifier and target cell.

Correspondingly, the mobile station determines the target cell from thistarget cell identifier included in the DCI.

Lifetime Parameter

As explained in the background section, compared to other TDDre-configuration methods based, e.g., on MAC or RRC, the TDDre-configuration by DCI/CRC of the present invention shall be in theorder of 10 ms. Of course, the dynamic TDD re-configuration indicationcould be valid for only one radio frame; however, this would require alarge overhead, since the same TDD re-configuration message would needto be transmitted every 10 ms.

According to a different solution, the DCI could include a lifetimeparameter indicating the amount of time the TDD re-configuration shouldbe valid. The lifetime parameter may be implemented in various ways, andcan have a length of various bits.

Using a lifetime parameter of only 1 bit, allows distinguishing betweentwo periods for which the TDD configuration shall be valid; e.g., 10 msand 40 ms, i.e., 1 radio frame and 4 radio frames. One radio frameappears to be the shortest reasonable valid time for such a dynamic TDDUL/DL re-configuration. 4 radio frames is equivalent to an MB SFN(Multicast-Broadcast Single Frequency Network) interval. Of course, anyother time values than 10 and 40 ms may be defined, such as 100 ms or200 ms. 200 ms, i.e., 20 radio frames, is equivalent to the RRC timescale for TDD re-configuration. Thus, the gap between the TTre-configuration time scales using the PHY-layer (i.e., DCI/CRC) and theMAC/RRC layer can be closed without losing potential to quicklyreconfigure.

Using more than 1 bit, i.e., 2 bits or more, for the lifetime parameternaturally allows a more flexible TDD re-configuration.

Thus, the mobile station determines the amount of time the dynamic TDDconfiguration, indicated by said DCI/CRC, shall be applied.

HARQ Instruction

The HARQ instruction, for instructing the mobile station(s) to reset ornot the HARQ protocol upon applying the new TDD configuration, relatesto the problem caused by the change of TDD configuration, as will beexplained in connection with FIG. 14.

For illustration purposes it is assumed in FIG. 14 that a TDD UL/DLconfiguration #3 is applied to radio frame n, and a TDD UL/DLconfiguration #5 is applied to the next radio frame n+1. As depicted,subframes 3, 4 change from uplink to downlink. Correspondingly, thenumber of HARQ processes or the timing relation for UL HARQ can change,when reconfiguring the TDD UL/DL subframes, as can be seen in TS 36.213section 7 (with Table 7-1), section 8, section 8.3 (with Table 8.3-1),and section 10 including subsections, particularly subsection 10.2. Incase there are fewer HARQ processes, the UE cannot know which process iscontinued and which earlier PDCCH is the reference for the NDI (New DataIndicator) toggling. Some of the resulting problems will be discussed inmore detail below.

The HARQ procedure for PDSCH received in subframes 7, 8 and 9 of radioframe n is showing ambiguities. The ACK/NACK feedback for the assumedPDSCH transmission in those subframes 7, 8 and 9 can no longer beperformed correctly, since the subframes 3 and 4 of radio frame n+1 dono longer allow sending the PUCCH with the ACK/NACK feedback.

The HARQ parameter can configure the HARQ behavior in the mobile stationupon applying a TDD UL/DL re-configuration.

A first option is that the HARQ instruction instructs a complete resetof the HARQ protocol, such that all subsequent transmissions aretriggering a new transport block. Implicitly, the HARQ buffers areflushed, i.e., deleted. The advantage is that the corruption of the HARQbuffers can be avoided.

This first option can be specified by the following procedure. The NDIsfor all uplink HARQ processes are set to the value 0. The soft buffersfor all downlink HARQ processes are flushed. For each downlink HARQprocess, the next received transmission for a transport block isconsidered as the very first transmission.

The second option for the HARQ instruction parameter is that the HARQprotocol is no reset. Thus, the HARQ buffers are kept to enablecontinuation of the HARQ protocol across TDD UL/DL reconfiguration so asto optimize throughout performance. This if beneficial, if most HARQprocesses according to the old TDD configuration have completedsuccessfully at the time of the TDD re-configuration.

Therefore, there is a trade-off between the first and second option, andthe base station may set the HARQ instruction to one of the two. A HARQinstruction field of 1-bit suffices in this preferable case.

Therefore, the mobile station determines how to behave regarding theHARQ processes, from this parameter.

Padding Field

The padding field may be inserted into the DCI with a pre-defined valueknown to the mobile station as well as the base station and in orderthat the mobile station may determine whether the padding field takesthe value as pre-defined. If the DCI comprises the padding field withthe pre-determined value, the mobile station may determine that thereceived DCI indeed transports the TDD UL/DL re-configuration.Therefore, the padding field allows the mobile station a second time todetermine that the DCI transports the TDD UL/DL configuration; not onlyby the TDD RNTI (first embodiment), the SC-RNTI (second embodiment), orthe invalid parameter in the DCI (third embodiment).

The padding field is included preferably in a DCI of a 3GPP Format, suchas the Format 1C, in order to exploit the remaining bits of the DCI,that may not be used for any of the other parameters. The padding fieldcan thus have a length of 1-32 bits. When using a DCI of a particularsize, and after deciding and setting the particular additionalparameters to be included in the DCI, often there will be bits remainingthat would not be otherwise used. Therefore, to exploit these bits aswell, padding field is used.

The term “virtual CRC” may also be used by the skilled person todescribe such a padding field with determined bit values.

Thus, the mobile station can compare the value of the padding field withthe pre-defined value to ensure that the DCI carrying said padding fieldindeed is intended for carrying the dynamic TDD re-configuration.

Buffer Status Report (BSR)

BSRs from the mobile station to the base station are used to assist theallocation of uplink resources. Generally, the more buffer is filled atthe mobile station, the more resources or more frequently resourcesshould be assigned to that mobile station for uplink transmission.Details can be found in LTE—The UMTS Long Term Evolution—From Theory toPractice, Edited by Stefanie Sesia, Issam Toufik, Matthew Baker, Chapter4.4.2.2.

The reporting of BSRs is a MAC function, which implies that thecorresponding transport blocks on the physical layer are subject to theHARQ procedure with possible retransmissions. A BSR can be triggeredunder several circumstances, amongst which is the expiry of a‘periodicBSR’ timer. Details can be found in LTE—The UMTS Long TermEvolution—From Theory to Practice, Edited by Stefanie Sesia, IssamToufik, Matthew Baker, Chapter 4.4.2.2, incorporated herein byreference.

As mentioned, upon applying a TDD reconfiguration there could be someunclarity or confusion between mobile station and base station as to thestatus of the HARQ protocol. In the case of transmission of BSR, therecould be therefore a misunderstanding if a BSR is part of an uplink(re)transmission after a TDD reconfiguration. Therefore, the mobilestation may receive a parameter to let it know whether the BSR procedureshould be reset, which may imply one or more of the following:

-   -   cancel or restart pending (re)transmissions of BSR    -   reset/restart the ‘periodicBSR’ timer    -   reset/restart the ‘retxBSR’ timer

Scheduling Request (SR) and Random Access Channel (RACH) Procedure

In case the mobile station intends to transmit a BSR but no or notsufficient uplink resources are available to transmit the BSR, themobile station can transmit an SR to the base station on PUCCH or byusing the RACH procedure. Details can be found in LTE—The UMTS Long TermEvolution—From Theory to Practice, Edited by Stefanie Sesia, IssamToufik, Matthew Baker, Chapter 4.4.2.2, incorporated herein byreference. Since the timing when a PUCCH might be transmitted for areceived PDSCH transmission is generally affected by a TDDreconfiguration as shown in FIG. 14, and the RACH procedure may extendbeyond a radio frame, i.e., be affected by a TDD reconfiguration due toa change of the location and amount of available DL and UL transmissionopportunities to complete the whole RACH procedure, it can be saferagainst errors to tell the mobile station that it should cancel orrestart the SR and/or the RACH procedure anew after applying the new TDDconfiguration.

Power Headroom Reporting (PHR)

Similar to BSR, the PHR is used to manage the uplink transmission powerof the mobile station. The base station can use the PHR to determine howmuch more uplink bandwidth per subframe a mobile station is capable ofusing. Details can be found in LTE—The UMTS Long Term Evolution—FromTheory to Practice, Edited by Stefanie Sesia, Issam Toufik, MatthewBaker, Chapter 18.3.3, incorporated herein by reference.

Since the available uplink transmission power per subframe needs to bedistributed across the assigned uplink bandwidth, this is equivalent toa power headroom report. A PHR is triggered, e.g., when a significantchange in the estimated path loss since the last PHR is detected, orwhen a configured time since the previous PHR has expired (‘PHR prohibittimer’), or when more than a configured number of TPC commands has beenimplemented by the mobile station.

Similar to the BSR, the PHR is transmitted as a MAC information inassigned uplink resources, and therefore the procedure can be affectedby a TDD reconfiguration. Therefore an additional parameter can tell themobile station that upon TDD reconfiguration it should do one or more ofthe following:

-   -   cancel a pending PHR report    -   trigger a new PHR report    -   reset/restart the PHR Prohibit Timer    -   reset the TPC command counter or set it to a defined value        Hardware and Software Implementation of the Invention

Another embodiment of the invention relates to the implementation of theabove described various embodiments using hardware and software. In thisconnection the invention provides a user equipment (mobile terminal) anda eNodeB (base station). The user equipment is adapted to perform themethods described herein.

It is further recognized that the various embodiments of the inventionmay be implemented or performed using computing devices (processors). Acomputing device or processor may for example be general purposeprocessors, digital signal processors (DSP), application specificintegrated circuits (ASIC), field programmable gate arrays (FPGA) orother programmable logic devices, etc. The various embodiments of theinvention may also be performed or embodied by a combination of thesedevices.

Further, the various embodiments of the invention may also beimplemented by means of software modules, which are executed by aprocessor or directly in hardware. Also a combination of softwaremodules and a hardware implementation may be possible. The softwaremodules may be stored on any kind of computer readable storage media,for example RAM, EPROM, EEPROM, flash memory, registers, hard disks,CD-ROM, DVD, etc.

It should be further noted that the individual features of the differentembodiments of the invention may individually or in arbitrarycombination be subject matter to another invention.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present invention asshown in the specific embodiments without departing from the spirit orscope of the invention as broadly described. The present embodimentsare, therefore, to be considered in all respects to be illustrative andnot restrictive.

The invention claimed is:
 1. A mobile station operable in one of aplurality of Time Division Duplex (TDD) configurations in acommunication system, the mobile station comprising: a receiver, which,in operation, receives a system information block (SIB) that includes adefault TDD configuration defining uplink, downlink and specialsubframes within one or more radio frames, each radio frame includingmultiple subframes, and receives downlink control information and acorresponding error detection code for the downlink control information,wherein the error detection code is scrambled by an identifierassociated with the mobile station, processing circuitry, coupled to thereceiver, which, in operation: in response to successfully decoding thedownlink control information with the error detection code scrambled bythe identifier, determines a TDD configuration, among the plurality ofTDD configurations including the default TDD configuration, based on thedownlink control information, determines at least one serving cell, towhich to apply the determined TDD configuration, applies the determinedTDD configuration to a radio frame n+1 in the at least one serving cell,wherein n corresponds to a radio frame in which the downlink controlinformation and the error detection code are received by the mobilestation, and in response to expiration of the determined TDDconfiguration, applies the default TDD configuration to a radio framen+1+x, where x is a positive integer.
 2. The mobile station according toclaim 1, wherein x is 1, 2 or
 4. 3. The mobile station according toclaim 1, wherein the communication system is a LTE communication system,and the downlink control information is a downlink control informationof format 1C.
 4. The mobile station according to claim 1, wherein thedownlink control information includes an invalid parameter with one of aplurality of invalid values, and the processing circuitry, in operation,determines one of the plurality of TDD configurations based on one ormore of the invalid values, wherein the one or more of the invalidvalues indicate at least one of the following: the indicated TDDconfiguration, a HARQ instruction to reset or to not reset, uponapplying the indicated TDD configuration, a HARQ protocol of the mobilestation for the serving cell to which the indicated TDD configuration isapplied, a lifetime parameter indicative of an amount of time for whichthe indicated TDD configuration shall be applied, a buffer status reportprocedure instruction, instructing to cancel a pending buffer statusreport procedure or to trigger a new buffer status report procedure,upon applying the indicated TDD configuration, a scheduling requestprocedure instruction, instructing to cancel a pending schedulingrequest procedure or to trigger a new scheduling request procedure, uponapplying the indicated TDD configuration, a random access channelprocedure instruction, instructing to cancel a pending random accesschannel procedure or to trigger a new random access channel procedure,upon applying the indicated TDD configuration, and a power headroomreporting instruction, instructing to cancel a pending power headroomreporting or to trigger a new power headroom reporting, upon applyingthe indicated TDD configuration.
 5. The mobile station according toclaim 1, wherein the downlink control information indicates at least oneof the following: the TDD configuration, to be applied to the at leastone serving cell, in a TDD configuration field, a HARQ instruction,including an instruction to reset or to not reset, upon applying thedetermined TDD configuration, a HARQ protocol of the mobile station forthe serving cell to which the determined TDD configuration is applied, alifetime parameter for the determined TDD configuration indicative of anamount of time for which the determined TDD configuration shall beapplied, a padding field bit value, which is or is not identical to apre-defined bit value, a buffer status report procedure instruction,instructing to cancel a pending buffer status report procedure or totrigger a new buffer status report procedure, upon applying thedetermined TDD configuration, a scheduling request procedureinstruction, instructing to cancel a pending scheduling requestprocedure or to trigger a new scheduling request procedure, uponapplying the determined TDD configuration, a random access channelprocedure instruction, instructing to cancel a pending random accesschannel procedure or to trigger a new random access channel procedure,upon applying the determined TDD configuration, and a power headroomreporting instruction, instructing to cancel a pending power headroomreporting or to trigger a new power headroom reporting, upon applyingthe determined TDD configuration.
 6. A method executed by a mobilestation operable in one of a plurality of Time Division Duplex (TDD)configurations in a communication system, the method comprising:receiving a system information block (SIB) that includes a default TDDconfiguration defining uplink, downlink and special subframes within oneor more radio frames, each radio frame including multiple subframes,receiving downlink control information and a corresponding errordetection code for the downlink control information, wherein the errordetection code is scrambled by an identifier associated with the mobilestation, in response to successfully decoding the downlink controlinformation with the error detection code scrambled by the identifier,determining a TDD configuration, among the plurality of TDDconfigurations including the default TDD configuration, based on thedownlink control information, determining at least one serving cell, towhich to apply the determined TDD configuration, applying the determinedTDD configuration to a radio frame n+1 in the at least one serving cell,wherein n corresponds to a radio frame in which the downlink controlinformation and the error detection code are received by the mobilestation, and in response to expiration of the determined TDDconfiguration, applying the default TDD configuration to a radio framen+1+x, where x is a positive integer.
 7. The method according to claim6, wherein x is 1, 2 or
 4. 8. The method according to claim 6, whereinthe communication system is a LTE communication system, and the downlinkcontrol information is a downlink control information of format 1C. 9.The method according to claim 6, wherein the downlink controlinformation includes an invalid parameter with one of a plurality ofinvalid values, and one of the plurality of TDD configuration isindicated by one or more of the invalid values, wherein the one or moreof the invalid values indicate at least one of the following: theindicated TDD configuration, a HARQ instruction to reset or to notreset, upon applying the indicated TDD configuration, a HARQ protocol ofthe mobile station for the serving cell to which the indicated TDDconfiguration is applied, a lifetime parameter indicative of an amountof time for which the indicated TDD configuration shall be applied, abuffer status report procedure instruction, instructing to cancel apending buffer status report procedure or to trigger a new buffer statusreport procedure, upon applying the indicated TDD configuration, ascheduling request procedure instruction, instructing to cancel apending scheduling request procedure or to trigger a new schedulingrequest procedure, upon applying the indicated TDD configuration, arandom access channel procedure instruction, instructing to cancel apending random access channel procedure or to trigger a new randomaccess channel procedure, upon applying the indicated TDD configuration,and a power headroom reporting instruction, instructing to cancel apending power headroom reporting or to trigger a new power headroomreporting, upon applying the indicated TDD configuration.
 10. The methodaccording to claim 6, wherein the downlink control information indicatesat least one of the following: the TDD configuration, to be applied tothe at least one serving cell, in a TDD configuration field, a HARQinstruction, including an instruction to reset or to not reset, uponapplying the determined TDD configuration, a HARQ protocol of the mobilestation for the serving cell to which the determined TDD configurationis applied, a lifetime parameter for the determined TDD configurationindicative of an amount of time for which the determined TDDconfiguration shall be applied, a padding field bit value, which is oris not identical to a pre-defined bit value, a buffer status reportprocedure instruction, instructing to cancel a pending buffer statusreport procedure or to trigger a new buffer status report procedure,upon applying the determined TDD configuration, a scheduling requestprocedure instruction, instructing to cancel a pending schedulingrequest procedure or to trigger a new scheduling request procedure, uponapplying the determined TDD configuration, a random access channelprocedure instruction, instructing to cancel a pending random accesschannel procedure or to trigger a new random access channel procedure,upon applying the determined TDD configuration, and a power headroomreporting instruction, instructing to cancel a pending power headroomreporting or to trigger a new power headroom reporting, upon applyingthe determined TDD configuration.